I identified 2 reasons why I thought the white griffins' actions were logical:
1. Unit Placement
...depending on the placement, if the centaurs are in the 1st or 6th slot (elves in the 3rd)
or the elves are in the 6th, and the centaurs are in the 3rd - then they would definitely not attack the elves in the first round... but with other placements, they sometimes attacked the elves.
2. Strength of the elf stack
...according to the save, it was approximately 32, and there is an opinion that the griffins either specifically feared the elves (counter-attacks) or simply the counter-attack from the elves was stronger than from the centaurs.
3. Hero
Ivor is a specialist in elves, who buffs them... increasing the effect of point #2
P.S. I think I heard something similar when analyzing the capture of mermaids, etc., when dragons are afraid to attack a stack of trolls, for example, if their number (stack strength) is greater than a certain number... the same applies to angels.