No, I had not watched that video. But after watching it I still do not get it why you say 2001 for Australiawhereas this was even said in the video to be the overall production?
What Ian doesn't mention in this video, the BritishWWI sniper rifles had the serial number STAMPED to the rear sight base whereas the Irish ones had the serial number ENGRAVED to the side of the rear sight base. Also the Irish ones had the serial number with W prefix whereas the British WWI ones had the serial number only (he in fact said that wrongly in this video - the proof to that is available in our knowledge base here: No.3 MkI* (T) Rifle (PP Scope) ). Hence it could well had been the Australians "just prefixed" the WWI British sniper rifles with their inventory numbers and adding the ownership stamp from this period - would make sense to put their stamps on the guns, so that in war they clearly can claim what is theirs. Maybe that was also connected with an overaul, IDK. Maybe I missed it, but didn't see any evidence for any other manufacturer being used other than Winchester, just them mentioning that "such rifles turned up".
PS: just at this point, another big telltale for the Irish contract BSA P.14 snipers is the shape of the front base which is much more square when looking at it from the side, especially at the rear end, when comparing it to the WWI bases. Also the Irish rifles all have a dull surface and a blueing which looks dip blued whereas the WWI rifles have a polished surface with blue color blueing.
Edit: stop the YouTube Video at 03:09 and compare the font of the prefix versus the font of the rifle serial. The "2" of the prefix is a different font than the two "2's" of the serial following. I think this would clearly indicate the prefix was stamped at a later point and not at the same time.