I guess there are two types of people on this world, the ones who think CR is a useful DM tool, and the ones who think about their encounters. Maybe I wasn't clear enough when I said that pre-built stat blocks are a shortcut, they're there for you if you aren't able to give it the time they need, and they certainly do follow the rules of the game, even if they don't have player classes, everything there conforms the the rules of the game (in third edition of course there were NPC classes, I suspect they still exist). I'm almost uncertain what we're talking about now, but if you made that veteran a different class or race then yes I would expect you to modify his abilities and because that veteran has no race, I would expect you to give him one, just don't tell me you're building NPCs that way. Honest question, how do you make NPCs?
I don't read as many D&D blogs as I used to but here's a pertinent one that I read a number of years ago that I liked a lot Calibrating Your Expectations an unmodified commoner is not only important it is more or less fundamental to this whole discussion, it's a d20 system by which the Vitruvian human commoner is the measuring stick of every dice roll, by making every race align with that 10 ability array, you're making them all conform to that mold. I think Justin revisited this post when 5e first came out which is also pertinent, but I don't have that bookmarked.
Matthew Colville, who I don't often agree with as a DM, also had an interesting video on encounters and stat blocks, but I can't remember where that was, if I find it in time I'll edit it in.
