It’s obviously something you can do but I wouldn’t recommend it as normal practice. In some types it could bite quite badly at low level, especially if you were a bit on the slow side.
It’s a useful technique if you’re undershooting with no increase in power available and still have some air underneath you. Bear in mind that the initial effect will be for the undershoot to worsen before it gets better.
The pilot in the OP seems to have decided on a land flap setting, then changed it on the way down for reasons not much connected with airmanship. Although it probably didn’t matter in this instance, it’s a sloppy way of doing things and if it became a habit, could cause problems on limiting runways. Stable approaches aren’t just a good idea for airliners...