As you can see, no easy answer....
It can be:
Normal consitution of the person. In fact to see if you really have got low blood pressure you should have a reference point for it.
It could be the fact that he is an athlete. good examples come from long distance swimmers. So it even depends on the sport.
It could be the weed or a particular interaction from that strain with him
It could be the medecines he is tacking or the simple fact that he is recovering from surgery.
For him would be quite easy to state out wich one beacuese, if he is fealing low blood pressure dizziness for the first time, he has only got to realize what's the new event in his life.
Personally i get low blood pressure from cannabis. but it depends on wich strain i smoke. Really.
Ah, if he is getting anti inflammtory drugs, and with knee surgery he must have, certanly he has got low blood pressure. Wich becomes more evident when the effects of the drugs lays off. And remeber that the shite that suppress inflammation usually stays in your system for more then one month.
Btw, how can you falks smoke and be athlete, it really is a mistery for me.
Every time i swmmed seriously in my life, i had to quit smoking!
Gee, i envy you people