It's certainly a useful guide but be careful not to interpret it too prescriptively. A genuine L42 may have had it's 19T bolt head replaced by a non-engraved but perfectly fitting example in civilian ownership; a genuine rifle might be encountered occasionally with a machined pattern butt swivel - just a couple of examples. Also, PH were by no means the only suppliers of foresight protectors - many 4T's bore Singer manufactured examples (eg SM42, SM43, N67) & unless they were unserviceable they probably continued to 'wear them' in L42 guise.
Please don't think I'm criticising - just saying use lists such as this as a guide, but don't jump to too many conclusions if one particular detail isn't quite as your list says it should be - ask on the forum if possible, as someone will certainly be able to help. None of us want to be caught out by a fake, but, ironically, I find myself giving opinions to people increasingly frequently of late, where they suspect fakery in a perfectly correct rifle.
Just my tuppence worth.
ATB.