Originally Posted by Drip

Shine Crystal drop rate is definitely of the A+B version. At least, at the start of combat, my squad with Cactace, Peach and Strawberry Candle shows "Shine drop rate 50% increased" for all members.
Moonvine + Tachibana also results in a 2.4 (A+B) skill activation rate notification on the third turn.

However, there IS something different about the effect Geranium and Cyrtanthus have: they're affected by the affection statistic. So that might be either a bug or intentional, that the second effect of the two simply overwrites the first. This is definitely something worth investigating. Still leveling Cyrtanthus here, and she hasn't even evolved yet, so it might take me till next weekend before I can really look into it.

Can we actually be sure without stacking to a theoretical 100% (if it's A+B) or stacking to at least 50% and running a hundred battles? Or does it show on the in-battle text (I usually have FF on so I'm not paying attention)?

Also, it MIGHT be 3rd turn Activation + is A+B while 1st turn is A*B due to the fact you're taking hits the first two rounds. IDK, some testing would be required.

As for the affection based, IDK if that works differently.

I have put Geranium and Cyrtanthus in a team and play with them for a while. Skill Activation x1.2 only happens in the beginning of each battle and it doesn't involve A+B or A*B algorithm I think. It may overwrite each other, as someone said.