It seems pretty clear that these rifles represent experimentation that was going on. By 1931 had the Soviets not settled on using the Mosin-Nagant as their sniping rifle? I'm not a student of the M-N, but IIRC the first PE/PEM scopes we see are dated 1931? So perhaps by the time the movie was made, these Ross and P14 models were no longer under consideration and effectively just experimental "left-overs" which could be used without divulging any secrets.
As in my previous, we don't know exactly why they were using Rosses (and P14s), but we can hypothesize. One other reason the Ross is suitable for sniping is that the straight-pull action requires less obvious movement to operate the bolt, in particular no need to raise the hand/arm to rotate the bolt. A good deal of work was done at RSAF Enfield to develop a straight-pull sniping rifle, apparently just for this reason. To use the Ross action was of course "politically unacceptable"
IIRC the CEF turned in most of their small arms before leaving the Continent or the U.K. in 1919. Probably some SMLE's and Rosses were brought back to Canada, but I suspect all the SMLE snipers were returned to U.K. stores from where they had been issued. There is no record of them being in Canada post-WWI, unlike the Ross-Warner & Swasey rifles and scopes which were in store here until WWII (except for WWI losses of course). Most of the sniping rifles used by the C.E.F./Canadian Corps were Rosses fitted with Winchester A5 scopes by Canadian armourers; the scopes being purchased directly and possibly supplied from UK purchases as well. AFAWK, except for some examples in museums, the Rosses with A5 scopes were scrapped after WWI.
The Canadian Dept. of Militia & Defence would have had no part in deciding what the British War Department sent to Russia unless such weapons came from Canadian sources and there is no evidence that any did.
It is unlikely that any Ross sniper rifles accompanied the Canadian Siberian Expeditionary Force, (sent at British request) and even more unlikely that any such arms were handed over to the White Army. Certainly not the Warner & Swasey rifles as we have precise counts for those.
Well, let's think about this: if the Red Army began to study sniping in the early 1920s, and received training or at least training materials from the Reichswehr, we can be pretty sure they being both thorough and untrusting of "imperialist" states like Weimar Germany, would also do their own research. That research would naturally involve first all the open-source material available, of which H-P's book was the most well-known and detailed, though not the only by any means. So logically they had those books in hand by the mid-20s at the latest. As I mentioned, it's quite possible that materials on sniping were provided to Imperial Russian military missions and attachés during WWI. Touring sniping schools was a popular diversion for senior officers and foreign guests etc. after all. Considerable effort was put into helping the Russian Army before the Bolshevik coup in October 1917; I expect we provided them with all sorts of training and tactical materials and instructional manuals etc. Quite possible that the Bolsheviks acquired those materials after they took over, and by the early 1920s would have had time to start digesting such materials.
As you may know, Stalin's purges more or less destroyed the officer corps of the Red Army in the late 1930s, so those who oversaw developments in the 1920s and up to the mid 1930s, were mostly dead or imprisoned after 1937. True, some survivors were released from the Gulag to fight, such as Marshal Rokossovsky who emerged minus some finger nails, but I'm not sure how many overall. As far as I can tell, Gen. Morozov/Morozoff may have been a senior officer on the Northern Front in 1942, and he may have been cited in the article because he had something to do with the development of Red Army sniper doctrines, or just because he had an aristocratic sounding name that might have been thought to resonate better in the West
H-P's book may have played a notable part in the development of Red Army sniping doctrines, but the Red Army hung by a Lend-Lease thread in 1942 and it was wise to be polite to temporary allies like us. It was never Soviet custom to admit any technical debt to "imperialists", so it's doubtful such an "interview" was ever published in the Russian-language press in the USSR. No one in the West would quibble about that in 1942 either.
Not to say that H-P's book was of no value, but it is a general interest review of the subject after all. As much or more interesting material is found in Eric Parker's biography of H-P, which the Soviet's "friends" in the West had also no doubt purchased on their behalf, along with whatever else was thought potentially useful. One point that suggests some influence is the Red Army doctrine of snipers working in pairs, which AFAIK was never the German practice.
As for the P14 in the movie it appears the scope is a long eye-relief model set forward of the boltway perhaps to address the perpetual problem of loading the magazine with a scope in the way, but looking more closely it is probably just something made up for the movie to contrast with what the hero using. Straps have never worked well as a method of holding scopes onto rifles!
One of the few advantages of the Winchester A5 was that it could be slid forward in the mounts to allow the Ross to be clip loaded.