I have been curious about this myself and i believe the answer is, the catch up mechanic.
Blizzard made it so that each weekly reset after the BFA launch the amount of exp required per level on the heart of azeroth reduced by 30%
i imagine though that they kept a cap of say 1000 AP as you stated above, so it just means that we are so far into the expansion now that twinks can get insane Ilevel on their neck pieces without even really trying that hard