The Pencil 2 was replaced by the Pencil Pro (you can think of it essentially as the Pencil 3) quicker than the Pencil 1 was replaced by Pencil 2*, because of the larger iPads’ switch to landscape camera, which everybody clamored for. The new camera location made the iPads incompatible with the Pencil 2 for charging/sync so Apple had to introduce a new flagship Pencil. Apple still sells the Pencil 2 for older/preexisting iPads, just as they still sell the Pencil 1 for the same reason, but in order to move away from the legacy Pencils, Apple has to make all new iPads (except standard iPad which only uses the lower tier USBC Pencil) compatible with Pencil Pro, which because of conflicting hardware means they can’t be compatible with older Pencils. As another user said, this will upset people who have older devices, but not doing this would upset people with newer devices. But this is always what happens during these transitions from legacy tech.
I completely understand why Apple are adding support for the Pencil Pro, as you clearly explain.
But that does not mean they also have to remove support for the Pencil 2.
Even though it might not be able to charge from the new iPads due to the repositioning of magnets, there is absolutely nothing technically to prevent it from still being able to write on the new iPads. That simply requires the screen/pencil tip and bluetooth.
Pencil 2 users can still charge their pencils on their older devices, so they should still be allowed to use them to WRITE on the new iPads.