It doesn't say anything about lowering AP acquisition now since the game interface and definitions has been tweaked and improved. But back then the Viking Lore's skill definition was "Raises max HP/ATK. Lowers AP acquisition."
EarthCrust
Viking Lore does not show the effect description "lowers acquired AP" anymore. So does that mean it now just raises max ATK/HP? or it still has the "lowers acquired AP", just hidden?
The AP lowering does appear to still be a thing. I quickly tested this on one of the new maps that had a single unit (7-2-3)and attacked with Yerma from the same position (attacking from the side). With Viking Lore (Maxed) she went from 18 to 34 AP while without it she went from 18-39 AP. She has Job Crystal attached so it's a bit higher than normal gains either way but there is still a difference
Are you sure you tested correctly? You do know that hitting an enemy from it's sides or behind them grants slightly more AP than you would if you straight up hit them in the face, yes?