Often a task ends up requiring much more work than expected, or some more important task displaces sprint work, or you need to do something like prototyping or design work or customer consultation which can't be expressed well in terms of concrete deliverables. An environment where your boss is going to call you to account for only getting 2 points done last sprint when you were supposed to do 10 creates nasty incentives to avoid these things in favor of small easily-defined tasks.

Story points are fundamentally arbitrary to begin with. If you're doing development work that needs research and problem solving instead of just cranking out boilerplate for some standard type of application you've built 100 times before then often you can't even give a reasonable estimate for new work in terms of story points until you've already done most of it. That's the nature of creative and exploratory work.

So yes the kind of process that plans everything in two week sprints and tracks tasks lasting maybe just a few hours each via daily meetings is micromanagement. That's what it's called when managers are so incapable of setting a clear direction and then trusting their people to get the job done that they have to check up on progress several times every day and constantly meddle with the real work.

Generally the team agrees on the points of the tasks together. Investigative/research work is also pointed/estimated.

It's mostly for planning, though.