No hello is very reasonable, but only to a point. It's a specific adaptation to asynchronous communication that kicked off in the IRC days where channel idling was common - async is a radically different form of comms to in-person & this etiquette aids in adapting to those differences.

But it's important to remember that it is an adaptation for a specific comms medium & applying it too broadly may really just be a way of shirking socialisation. That's fine if you're most productive as an engineer working alone on your fully-self-contained owned project, but in most cases collaboration is beneficial. Collaboration introduces communication inefficiencies but its a known trade-off.

Especially extending this barrier-to-entry to other things like calls (verbal comms) & meetings (in-person) can lead to significant inaccessibility, exclusion & siloing. It's worth stepping back & looking at problems you may be trying to solve here: e.g. too-many-meetings or long meeting run-on. These are problems that frankly this doesn't do anything to solve whatsoever; you'll just end up with managers setting boilerplate agendas for the same "too many long meetings" & meanwhile some of the peers you may need to have a valuable short meet with will be too hung up by your requirements to contact you at all.