it works because in original immelmman you wantd to avoid attacking. attacking opponent planes with flwoer was never good idea, but defending with flower- now that this completely different thing which makes whole battle mechanic go south
so we fly in flower and redirect our planes makign sure they are flyign withotu settign up a patrol anywhere. we want to defend ourselves in flwoer formation without a need to attack. that decimated GO gumba on plane's test map that much he had to ask whole map to help him after he lost all planes.
so as such basic idea behind immelmman - use flower defense to cause dmg still works but ofc you will take some dmg now. losses should be 10-1 in your favor so I ma completely fine with that.
Yes flowering is still possible in general, this includes planes. I do not regard flowering as identical to the previously described immelman exploit though. It had a different underlying mechanic. For me it is important to give the same name only to the same mechanic, so that we don't get confused in discussions.
The flowering issue will only be fixed once we switch to the newer combat system sometime in the future.