I would say the reason is that not all boats porpoise. It is not the fault of the motor but the fault of the boat/motor combo. Your outboard fitted to another hull probably wont porpoise therefore there is no reason to change the design.
Its a common confusion that the motor is the fault, because it is the motor we modify to fix the fault.
Some motor to boat combinations just seem to fight eachother. Why? who knows.
The problem seems more evident in v-punts over 4 meters with decent size motors than with any other boat. Hornets have the same drama.
A commen fix for Hornets is to change the height of the motor to rectify porpoising, so it does'nt surprise me that when you altered the height, you got a problem.
I see Permatrim's as a last resort, and should not really be used until your sure your boat is set up right. Even then I dont like it. As far as I know they were originally designed to get a boat up on the plane quickly, good for skiers etc. Only in recent times do they seem to be used to cover up boat set up problems.
Its good that your boat now rides well, so I suppose they do have a place, and im sure many people will attest to their rectifying many issues.
Why did you change the motor height anyway ? was there a problem ?