Oh, they won't even need to be well-drilled on accounting to tell you that!
It's just what happens here.
But, yes, as has been said, there are a number of perfectly legitimate reasons, or even std accounting ones, for 2 signings to have been done and dusted but not officially signed/announced until a certain date.
On a related 'dates' theme, something that interests me (in my picky pedantic mode) was the appearance of FBS logo-ed shirts etc in the signing vids. Both Coady and Winks (not the New York detective series of the 70s) are wearing the pink FBS shirts... when we're led to believe that FBS was finished come 1 July. Clearly the vids were shot a day or so before the official announcement. On the day they vids were shot, FBS were official sponsors. On the day the vids were released, FBS were (we're led to believe) history. What gives there?
Btw, FBS are still listed as a partner on the club's website. And vice-versa. I wouldn't be surprised if they still have some sponsorship involvement.