Do I have to Connect my Calendar to Sembly?

It is not necessary. You can disconnect your calendar and invite [e-mail] as an attendee to each one of your meetings (here). You can also use an immediate invite form instead. Syncing calendars removes many issues related to inviting Sembly manually, like:

-inviting Sembly from the email that is not registered or aliased in Sembly and forgetting to add aliases;

-the constant need to remember to add [e-mail] to the meeting attendees;

-need to remember to open Sembly webapp and insert meeting details.