Depends on artist, venue, etc., since there are so many ways for them to get out without having to interact with anybody. Some bands and such will sign things on their way in to sound check in the afternoon, but it's really up to them. There is no standard answer.
If it's Ben Platt, then my take is that artists who include meet and greet options tend to bolt after the show, since if people wanted to see them, that path was made available... Also the dynamic has changed, since not everyone at DEH was a Ben Platt fan, they just wanted to see the show. Whereas pretty much everyone at his concert will be a Ben Platt fan, making the stagedoor less of an option. (If not Ben Platt/DEH, substitute any actor/show in there)