I’ve never arrived late to a broadway show either though I have been nowhere near attending 240! I can see how it would be incredibly disrupting if it is your row or right in front of you. I’ve certainly noticed the disruption - though from far back or side orchestra when it occurs in center orchestra close to the stage. Hard for anyone in the theater to miss those. I find though as you do the ushers wait for the lull, for after the main opening number is done, when people are usually still applauding, to minimize it. Of course if it is near you, or your row, however, the flashlight, the murmurs, and the need to stand up etc disrupt and break the magic, “lull” or not. Stuff is always happening on the stage once a show has started, at whatever point it is at....
i once saw an actor from the stage call out the latecomers - but it was completely in keeping with the character’s personality etc to improvise that into the monologue to the audience at that point. I am talking about Stephanie Block at The Cher Show. Right after the show’s opening number, when this couple is taking their center orchestra seats near the stage (effectively disrupting her and competing unintentionally for the spotlight) she started ragging on them, in good humor and in character, to laughs from the audience. I dont remember her exact words but as “Cher” she said “what are you guys doing here late? You missed a great opening number” Then something like “I guess you were busy eating a great dinner at some restaurant? ” or something like that but wittier. Obviously that’s a rare show, and timing point w/i the show, that let the actor use it.
In contrast I notice that often - if not always - plays strictly state no late seating. Thankfully.
I was once about 10 min late to NYCB - side / back orchestra - and we were not allowed in. I confess this upset me at the time mainly because our delay was caused by some unusual ticket pick up situation we were not aware of. We assumed the tix were at the Koch Theater box office but we were directed to that other building across the street where tkts is (not sure tkts was there at the time) so that added some walking to and fro to physically get these special price tickets, in hindsight the policy of no seating til intermission is a good one.