And there is also nothing wrong with a coach waiting to announce it either but people get worked up about it. I would guess he doesn’t like the way some head coaches deflect blame to other coaches by firing them immediately after the season.
As with everything, there is a balance. It was definitely the right move to wait until after the early signing period, so no problem with him waiting.
But they are announcing at least one new hire next week. So they have to know the simple question is coming: is the coaching staff complete? No real reason to keep it "secret"... right?