I've also observed the third direction, which is the message storm.
That's when someone breaks down their point into multiple separate messages, one sentence at a time, when a single coherent paragraph or two would have worked. Why send one message when you can send 7 in rapid succession?
It's arguably the most annoying method of communication because it spams your notifications and you have no idea when someone has finished dumping.
I think that is in line with what I said: a balance is best. I have seen the opposite of what you described: long messages with no paragraph breaks. Not great either.
Also, any metric ceases to be a good metric the moment it becomes a goal.
I have observed both of the above statements in many different contexts, they seem to be (somewhat) universal rules for human society.