You're right on the S&C coach primarily handling the training programs. I'll grant that I'm not familiar with the nuances of that, but I assumed that position coaches would be involved, especially with skill-focused stuff.
And I get that there's not that many kids left to sign, it just sounds weird. If you have all the guys locked up or close, why wait to make your coaching hires?
Maybe there's a handshake agreement to wait until after signing day, but hasn't conventional wisdom always been to get coaches signed up as soon as possible to help lock people down? I can't think of a situation where I've seen coaches intentionally wait for after signing day to leave a school, though I'm sure it may have happened. Bowl game, sure.
Maybe there's some grand plan, it's just that their stated justification strikes me as a really weird reason for waiting to make coaching hires.