If I buy a vintage bike it has to fit me, I see no point in buying a vintage bike that I can't take out and ride/enjoy/show off. The exception might be for something that was ridden by someone famous (or infamous) and has some provenance.
Ideally, it would have original parts but primarily it would be to ride, so I'm not going to get stranded in the middle of nowhere because something has crapped itself - so I have no trouble in putting on different components, or restomodding even. I hang onto the original parts though.
Whether anyone else is perturbed by the specs doesn't bother me, because here's the thing....
...an hour with a set of tools and a beverage of choice and all the stuff is swapped out.
The frame is a canvas for the parts to hang off. Don't get too caught up in it. Have at it.