I spent a long time trying to understand this situation:
and I still don’t get it!
Even regular 2-colour one-move-at-a-time Go can result in all sorts of weird and complex situations. Simultaneous-move multicoloured Go is so complicated, there must be all sorts of weird situations, and so little-studied (compared to standard Go) that there is probably not much precedent for resolving them. Incidentally, I believe this is one of @martin3141’s fields of study if I remember correctly.
For what it’s worth, when designing the game, I always picked the simplest option I could when faced with such decisions - for example using positional superko and Chinese rules. I imagine a similar approach would have to be taken for simultaneous move Go and, even then, I wouldn’t be surprised to encounter situations I hadn’t considered.