Most illuminating: the inventory display too is broken. Example:
Using 'CabePick'I checked UA 806 ICN-SFO for 5-13-19, 5-15-19, and 5-16-19.
Business is completely free on all three flights, according to the tool. However,

The economy seats sold/grayed out on all 3 flights ARE EXACTLY THE SAME:

41K, L; 43A, B, C, D, E.

This is a broken tool. Perhaps this is because of the Premium Economy inventory on this flight?

Sorry I cannot yet post screenshots, as I am a mere Noob.