Learn English – Is “he plays the piano” stative or dynamic

"I'm wearing the coat" means that I already have a coat on, not that I'm putting on a coat.

When wear is used in the imperative sense, typically what is meant that the person should arrive somewhere later with the clothing on already, or include the clothing as part of getting dressed fully, not immediately put on the clothing at that moment.

If for some reason someone wanted to tell someone to put something on using the word wear it would generally need a now with it - i.e. "Wear these gloves now."

I think you might be relying on gut instinct too much.

You can't know everything, let alone what he's saying.

In English, unlike languages that have methods of indicating and dealing with stative and dynamic verbs, there is little need for distinction. To complicate things further, English can approximate the "inchoative aspect", which indicates a transition into a state of existence.

All at once, she understood what her mother had always been saying.

The inchoative often has helping words like "suddenly" to indicate the transition into the state. This would explain sentences like:

I can't begin to understand what he's saying about the inchoative aspect.

or more simply:

I can't understand what he's saying.