even if they've heard it before, delivery can change it completely

I want to think the delivery probably made it hilarious

I imagine that if you hear the joke enough, it would end up having a meta-level of humour, similar to how cashiers joke about the silly people who say "does that mean it's free?" when something doesn't scan. In that case though, the jokes are at those customers who think they're funny, whereas in this case, the humour would partly come from being happy for the patients who are so tremendously psyched to get top surgery.

Hi I'm dumb but curious, what does "binding" mean in this context?

It might not be quite the answer you’re looking for, but generous fit around shapewear, torsos, and butts was a key feature of centuries of historical European men’s shirts. If your comrade can get down with ‘em stylistically, there’s a lot more variety than just stereotypical flouncy pirate shirts. For most of their heyday, they were typically worn tucked deep down in lieu of underwear.

I’m having a hard time tracking down a broad lesson on just historical base-layer linen shirts, but excellent historical gear merchant and YouTuber Townsends can show you some silhouettes. Don’t be freaked by what they’re charging, it’s premium priced srs bsns reenactment stuff. They made a little explainer video: https://www.youtube.com/watch?v=_FbwRSfedoE

The garment is reputedly a great beginner sewing project, or easy to crank out if you know someone really stitchy. Victorians used to buy them by the half-dozen or dozen. Here is a creator making one who mentions having top surgery: https://www.youtube.com/watch?v=lORt8kIwsNw

Shirts are one of those things that tend to look bad if they're not well fitted. I don't have much experience tailoring for people who are binding, but my experience making and modifying clothing for myself and others has led me to be one of those people who evangelise the benefits of getting high quality staple clothing tailored (though finding a good, reliable local tailor can be difficult for some).

The standard advice for shirts is to buy shirts that fit the shoulders, and then get them tailored. I don't know if that advice would still apply for people who are binding (I know that people with breasts often need to size up to allow enough space in the chest, and that may remain true when binding), but I would assume this would still apply.

You also mention fit issues around the butt. A transmasc friend reported that he had best success finding women's trousers that were in a more masculine style. He reported that although he struggled with gender dysphoria due to knowing they were women's trousers, how the clothing made him look caused to feel gender euphoria.

The Boob Cuttage