For this question, when triple buffs are mentioned, it's in reference to guaranteed triples or stacking buffs up to very high levels. Which is actually not that easy considering that kamihime abilities in this case are mostly in the same frame, so they won't be stacking with each other. It'll probably come down to 1 ability + barrage + union event buff + certain summon effects (Sandalphon and Icarus).

10% from Shingen's buff is actually pretty low in that context. Examples of higher triple atk buffs would be Krishna (40%) or SSR Baal (30%) (both Thunder). Brahma/Daphne/Thanatos can get over 50% triple. Tishtrya (light) can confer 50% triple atk to one ally.

So generally speaking, you won't accidentally be in position to actually have to worry about double attacks blocking triples. You more or less have to be intending for triples to be part of your game plan.