Slack in real time = I ran into a problem and I will bother you in real time until you fix it. Endemic to data scientists!
Not writing email = I need you to answer me now, not later. Also, I don't want to waste time composing text when I can just talk to you over video right now.
Meetings all the time = I want the highest bandwidth communication immediately, instead of having to wait for an unspecified length of time, only to realize that I have a follow-up question.
This is precisely about responsibility and responsiveness, right now, immediately, and in real time, until the problem is solved. It's very much a young person and startup thing. Maybe it works differently if you contract with a large, slow bigcorp of some kind, but I've never worked in such an environment.