After 6-8 weeks, a stroke has stabilized and the likelihood of its enlarging or becoming blood filled, are substantially reduced. Secondarly complications, if they were to occur, would occur at this time.
The next issue, is why the stroke occurred. If it can be arrested and prevented from reocurring, then the stroke becomes a non-issue if one can perform the physical demands of diving, the brain has a unique way of rewiring its functions and 'heal' any deficits that are more normal if the stroke is small [such as a lacunar infarct].
If the issue for causing the stroke cannot be fixed, then it can happen again. It is this factor that can prevent one from diving. For example, commonly strokes are causes by hardened arteries, and if so, it means that divers cannot exert themselves without causing added problems, including a heart attack. It may not be possible for such a candidate to dive.
OTAH, if the stroke was caused by a drug or chemical, and said agent was then removed, then there should be no reason for a repeat stroke.