I've had quite a lot of fish, over the years, that have displayed similar behaviour. It's mostly good old Pavlovian conditioning at work, IMHO
I might have mentioned before that our old oscar 'taught' my son to feed him (the oscar) on demand; he used to jump up and bang his condensation tray, my son would say, "oh, Gormok wants feeding", drop whatever he was doing and go give Gormok exactly what he wanted
And all the angels I've ever had have wriggled like puppies when they see me.
The cheeky Crown tail was a true rescue, I was doing a PC job for a client and he was living in an unfiltered 2 liter vase half dead, constipated and his fins were a mess they still are but hes a crown tail, and was going to be flushed down the toilet, So I took him home, that was 2 months ago, He has come a long way.