I ask before I take the interview. Location, salary range, linux laptop are prerequisites to me working for anyone. If they punt on the laptop question it means no and they are hoping you'll want the job even without. I can promise you I won't, and if you view that as a red flag I can promise I don't want to work there so I don't care.
If its a hard requirement for you just say that and say that's for workflow and you don't want to waste anyone's time
Kinda I guess, he's said he would hold back one part of a single shipment, but that is the absolute bare minimum