Actually VST 3.6.8. now implemented the same features:
https://sdk.steinberg.net/viewtopic.php?t=360&p=1215#p1215
kAmbi1stOrderACN, kAmbi2cdOrderACN, kAmbi3rdOrderACN
kSpeakerACN0...kSpeakerACN15
This should confirm to skip the W, X, Y, Z channels and replace with ambisonics0 to ambisonics15 or ambisonicsACN0... ambisonicsACN15