If he saw a doc and was fine, then I would lean towards the winstrol affecting his BP[without knowing his history and doing a check on him]. As far as the "only a 5 week BP raise not being bad"... there is no such thing. High BP is bad, period - especially if you knowingly contribute to it's rise. You never know what a higher BP can do, and if there is a weak link somewhere in a vein or artery that just needs a little push to start something bad.
I would never tell someone to knowingly take something to raise his/her BP abover normal unless medically warranted. This isn't the case.
If your friend knows he has BP issues, and knows the risks of As, and STILL wants to take them, then saying his priorities are backwards is a big understatement. Help him make the right choice for his health.
Safety first, everything else is secondary.
Hope I helped.