Strange. The point came without asking in an e-mail from the support about something else (a big patcher crashing). I have unfortunately lost many e-mails from 2012. However if it works indeed, everything’s fine then !
Just a note, I do think though that if you have nested poly~s with @parallel enabled, it only works on the parent poly~ (this may have changed in 6.1.x). For this reason (if I care about this in the particular patch I’m building), I tend to avoid nesting, if at all possible.