I'm not so sure about that. I literally just bought my X-S10 having also considered the X-T4, with using it as a webcam one of my primary considerations, and didn't see anything in the marketing materials to make it clear that one would work and one wouldn't.
If it was a marketing angle designed to push some buyers up to the X-T4, it's been executed hilariously badly.
I suspect it's a technical issue that will be addressed in time (and I'm grateful to have my Blackmagic to tide me over in the meantime, otherwise I would no doubt be SUPER shitty at Fuji right now).