I already fed my choco twice while stabled, no changes observed. Going to feed more and observe, will get post back here when I get results.
Update:
After I heard that you need to feed them when summoned, I tried feeding my chocobo ten Slykis Bud (after summoned), nothing happened either.
Going to try feeding ten while stabled, then summon and feed another one. Will update after I'm testing.
