"though it shows people going into the theatre wearing masks, assuming the audience for the filmed production"
The door that the masked people are entering says "Schoenfeld Stage Door", so I'd think the people we saw passing through it were masked cast and crew. The area they are in afterwards looks like a backstage area. The scenes depicted look like people reuniting. I'd think the footage is current, but you're right, we will have to wait.
Some of the original cast had already left. The actor playing Bob had some sort of vocal issue, and the ones playing Nick and Oz had left as well.