This was to be expected and made sense given the bylaws, but the NCAA made it explicit:
In baseball and basketball, a graduate student-athlete who qualifies for the one-time transfer exception but initially enrolls as a full-time student at the certifying institution after the first term of the academic year shall not be eligible for competition until the ensuing academic year.
This means that graduate transfers must be done in between academic years, not during one. It is a small detail which reinforces that these transfers are supposed to be academic in nature. Thus it makes sense for athletes to start graduate studies at the start of an academic year to get the benefit of the rule.