My guess is the Polaris tables found in the USNO's nautical almanac are for long term use. The Air Almanac Polaris table is recalculated every year. Pub. No. 249 Polaris table is recalculated for each epoch could be several years apart.
The following is from Pub. No. 249 Epoch 2020 Volume 1 page 17 (I've also attached the page)
Pub. No. 249 Volume 1
Go to page 17 of Pub. No. 249 and it'll explain the difference between the two tables.
Here it is by itself-
output.pdf (Size: 102.03 KB / Downloads: 309)
Lou
The following is from Pub. No. 249 Epoch 2020 Volume 1 page 17 (I've also attached the page)
Pub. No. 249 Volume 1
Go to page 17 of Pub. No. 249 and it'll explain the difference between the two tables.
Here it is by itself-
output.pdf (Size: 102.03 KB / Downloads: 309)
Lou