So the question is, have the Japanese noticed all the build up and made any changes to the invasion plans?
they did historically
Note that this PA is about 40,000 men (and 4 divisions) smaller than the historical one and the only non historical reinforcements are a division HQ, an infantry regiment and a horse cavalry regiment. The air element is about the same size in terms of fighters, although dive bombers have been switched out from the B17s (54 A24, 6 B17 vs historical 35 B17s) which is only about 25 more aircraft
What is important from their stand point is the hardening of the American airfields with revetments
So for now no changes in forces allocated