I can certainly understand Athos seeing only positives from his son becoming closer to (and maybe even eventually marrying) Lerunda in the future. The gryphons are living gods to them, and she's practically Saintess-level in importance from their point of view given she's like a chosen one living with divine beings.
Considering that this is one of those "abandonment" fantasy stories with implied comeuppance for those who abandoned her (premise says they chose the wrong person as the "shrine maiden") it's way more wholesome than I expected. I think I'd like it to stay this way so no sudden grimdark drama chapter please. We've already been introduced to the conflict from humans who raid beastkin villages for slaves, so there's the possibility a raid will come their way, but this time maybe the gryphons are powerful enough to stop them.