"the leaker has not commented on why DJI has abandoned the Action 2's form factor"
Because the Action 2 wasn't a logical descendent of the original model. The Action is compact, functional and compatible with the GoPro ecosystem in most ways. The Action 2 was gimmicky, difficult to use, tricky to make use in the GoPro ecosystem (although it can be) and bizarrely was hard to use as an action camera. It felt more like competition for the Insta360 Go or maybe for the Insta360 One... but weirder.
I love the Action, but skipped the Action 2. If DJI makes the Action 3 a direct upgrade to the Action, I would consider it.