I think you're right, I never thought about it before, but the comment after the thunder bagua calsh was "a clash of black lightning"
the fact that they only put that comment after the thunder bagua clash means this is the first time Yamato uses Adcoc in the manga & probably but not certainly this is the first time she uses it in her life, also note that the hollowed glacier slash & that attack when she hit Kaido in the face and said "shut up", these two attacks happened after the thunder bagua clash & she didn't use Adcoc, while the white snake rush attack was probably an Adcoc.