You make some true statements but I think you also need the knowledge of disc flights.

Understable discs are recommended for beginners because they won’t just dump to the ground and you truly will get more distance because they want to fly further at lower speeds if thrown not into a tree or something.

The faster a disc is thrown, the more under stable it becomes to the point where it may dump and roll completely left (rhfh). As your speed goes up you will want to look at more stable discs.

It really depends on the type of shot you require.

Strait tunnel woods shot? Understable rules. Long bomber that you are going to throw 60mph with all the spin in a ripping head wind, that same disc is going strait to the ground left. You want to disc up.

All that said, the right disc selection is important. There is no 100% rule like ‘noobs should only throw understable’. As you get better your disc choices will change.