I’m curious now, what would you view then as examples of both synch and async communication?

I think async and sync is more about expectations, with the caveat that a non-recorded zoom meeting is sync, while a recorded zoom meeting can be async. That being said, I feel it's my responsibility to have my notifications tuned properly so I'm not interrupted.

So to me synchronous comms are comms that can't be consumed asynchronously. The only text version of that I can think of is an exploding Signal message or similar. Any non-recorded video message is synchronous.

A key example of async communication are tickets/issues and merge requests.

Slack can be both depending on the situation

Calls are definitely sync, although I guess voicemail is async