Right as far as the spit or swallow thing it's about acceptance believe it or not.

Since the time we hit puberty dudes deal with a lot of what you'd call "emission shame." Male sexuality is shamed and demonized at just about every turn and it's worse when you're young. I.e., called pervs for the same behavior women get away with (see orlando bloom and Kit Harrington getting nudes leaked versus the fappening), the talking to if someone finds the proverbial cum sock is mortifying, and on topic: the cum dodger. Now imagine you have a woman who is already going so far as to put another frequently shamed sex object (your cock) in her mouth and when it's time to cum... that thing you're ashamed of? She happily gulps it down.

It's a really good feeling and it's not entirely sexual.

I think it's very much like the distinction between mechanical and IOP and even further the difference between IOP and actual passion. A mechanical provider isn't doing anything wrong but it's making it glaringly obvious that it's transactional. By the same token there's nothing wrong with a provider that doesn't want to swallow cum (and I'd wager many on here don't have the diet to make it tasty) but for a lot of guys that's not going to be a mark in your favor either.