DH and I have both been WFH for the last year and it's not obvious when either of us will be back in the office.
I've always had my own office in the past, and have struggled not being able to talk to myself, wander about when on the phone, and even just be quiet/still to think.
DH has always been in open plan offices and enjoys the company. He genuinely can't comprehend that I'd like my own space, and he takes it a bit personally.
We have a room that could be turned into a second study without it being a great loss.
Out of interest, how common is it to work in separate rooms?
YABU - partner and I work in the same room without wanting to work separately
YANBU - partner and I work in different rooms of the house (or absolutely would work in a separate room if one was available).