I went to the first performance of Waitress and people were definitely lined up like that, but as previously mentioned no one stops or engages other than a simple wave as they leave.
I also noticed security isn't telling them to leave, so I feel like if the issue was more pressing than security would in theory be asking them to leave or there wouldn't be any set up for it to begin with.
I mean, if people want to stand there and watch people leave, more power to them, but it seems like there's been no clear communication regarding things. I don't think Miguel's photos are any attempt to get people to come to stage door but merely a way to acknowledge people in a friendly way. I can see how it might lead to something like that, but again, I think the issue of it all hasn't been addressed from the higher ups.
"Anybody that goes to the theater, I think we’re all misfits, so we ended up on stage or in the audience.” --- Patti LuPone.