I'm just curious as if there were any expectations conveyed to the streamers that signed up for this jam. I noticed that all but one of them have been inactive for months and the one that is currently active isn't covering the games submitted for this jam. 

Were they supposed to cover the games between submissions closing and the voting period ending or just after the voting period?

Hi!
We notified all streamers on Tuesday. Almost everybody have responded that they will.
They are free to do it at any time (before or after the voting period), although we recommend them doing it within the month of June.
We will notify you on Twitter or BlueSky.
Thanks!