College BBall players can declare and then opt to return BUT they must opt to return in early April - actually one day before BBall signing day. The NBA draft isn't until June.

Conceptually, I wouldn't have a problem at all with players testing the water all the way through the draft and being allowed to return if they didn't like what happened (with the limitations of no agent or extra benefits). I don't find that any different than the random undergrad going on a job interview and then declining the position.

The problem is the timing. National signing day is in early February. The NFL draft is in late April. If players are allowed to return after signing day, you've got a roster management nightmare where virtually every major program will find themselves either short players because they assumed someone would return and didn't or over the 85 limit because some guy decided to come back.

The basketball deadline to withdraw from the draft and return is before the late signing period for this very reason.

There's a pretty easy solution for football, and that's to implement an early signing period (which IMO would help get rid of some of the flip drama we see every year) and then have a second late period after the NFL draft - but for some reason nobody seems to be a fan of an early football signing period.