Definitely agree with this. Both are plural, but all y'all is a direct address to a specific group of people. I might be chatting with people at work, standing

Definitely agree with this. Both are plural, but all y'all is a direct address to a specific group of people. I might be chatting with people at work, standing around getting a snack in the kitchen or, like you said, hanging out in slack general. And I might toss something out to the room, "Y'all want to go out to this comedy club on Thursday night?" But when Thursday night rolls around and 3 of us are waiting on 5 people to commit and log out, then it's, "All y'all need to wrap it up."