It's part of YC's Startup School. Did you sign up for SUS?
I have done SUS before and this had never happened to me. Did they change something recently that I am not aware of? There is also no mention of SUS anywhere inside the invite.
Yes, this SUS is a live course series. If you signed up this time, then you enrolled to join the live courses. There's a button somewhere to switch to the self service course if you can't or don't want to do the live version. They also did send out a few e-mails saying they will be sending calendar invites.
Are you implying that it's unreasonable to want to participate in Startup school and have a usable calendar?
Not every action you take involving a large company should sign you up for endless and unlimited bullshit which requires time to manage away.
No but they clearly state you will get invites to the live lectures every week.