What's clear from those in the know, there are many variations in sub-class and even individual locos, which is very interesting. This must make life really difficult for those creating sound files.
Speaking as a very average modeller, I'm not about to get hung up over such detail, though I can't deny I do like differing sounds from a loco class. As an example, on my old Scottish layout my 37/0s had a different start up to my 37/4s.