It definitely counts as an unreasonable change. If you quietly accept it, or quit due to it, you won’t get the help. If you set things up in your favor by replying to the mandate with language along the lines of ‘such a significant change to working conditions requires a renegotiation of my contract’ then you’re placing yourself in a good position to say that you were constructively dismissed, not that you quit.

A change from working wherever you are (which could be hours away if you were full remote) to the office is just as significant as being moved from one metropolis to another.