I said "a series of questions akin to", not "this single question". Please don't take my words out of context.

My comment isn't about source control. It's about warning applicants not to over-obsess about technical details when other stuff influences job happiness much more than git vs mercurial.

I think "what source control tool do you use" is fine, it's the "and why" where I start to think that you're asking the question to be combatative. I agree if you're expecting a couple word answer like Github etc, then perfectly good question to ask.

The why can be really important though. We do X because Google does it, or something like that is often a red flag because they have some insanely convoluted process that they don't need. knowing that things are selected that fit the size and scale of where a company is or will be soon is important.