mentors arent allowed in the final sessions for logistical reasons, the line has to be drawn somewhere as to who can participate and the fund investors seems like an obvious line.

Firstly, I don’t see why mentors are invited at all.

Most to all of the mentors have a vested interest in the startup community thriving, lawyers, marketers, investors and angels who were not part of the main fund but still get direct access to the startup, a phone call isnt going to help until you figure out who you are calling, thats where seedcamp and such events help