So you want every communication with you to have full context? Perhaps the manager needs a couple of things and wants to be respectful of your schedule. They might not know the full extent of the conversation yet. If you work in an environment where full context is necessary to combat paranoia then there are other problems. If you need to have every conversation be formal then don't expect to be the first person a manager talks to when they are thinking about things.

Let’s talk about our sexual harassment policy when you have a minute.

See it’s not some ungodly burden to add one or two words of context

Any manager who sends that message is an idiot. They are going to have an HR rep with them and tap you on the shoulder to go into a conference room. The whole idea of an environment that could be that bad is way worse than any message you could receive.

Frankly, someone disturbing my flow by adding information that I don't need now and making me subconsciously think about something new is now respecting my work.

That's an obvious strawman. You can include context without having to write an essay. If you have a few things to say then list those things.