Speaking as a pilot who positions a lot in the back as SLF I prefer not to have some idiot drop their overweight "handbaggage" on my head in the final minutes of the trip because they cannot wait until the a/c comes to a full stop at the gate to get their precious belongings.
Even after it is parked, it will take some time to open the door(s) and only then will anybody get off the a/c; not one second earlier.
So I applaud any Flight Attendant who enforces the logical rule of staying seated with your belt on until we're at the gate; I have also witnessed on occasion the effect of a quick dab on the brakes that is sure to get everybody's attention.
Using the slide to escape from his job was a bit OTT but at least he got a world wide debate going..