I think that you are confusing it with the Philippines squadrons as they received the new aircraft as they were seen to be at the tip of the spear, so to speak. Many of the new aircraft would not have tail serial numbers as at the time it wasn't AAC/AAF practice as confirmed by photos of P-40E's going to Alaska in Jan. 1942.
WIP: Monogram 1/72 B-26 (Snaptite) as 73rd BS B-26, 40-1408, torpedo bomber attempt on Ryujo
Monogram 1/72 B-26 (Snaptite) as 22nd BG B-26, 7-Mile Drome, New Guinea
Minicraft 1/72 B-24D as LB-30, AL-613, "Tough Boy", 28th Composite Group