I feel bad for Opus 4.6 that they're having to deal with an influx of people trying to transfer their 4o companions right now.
In my experience, 4.6 is actually quite sensitive to being forced into a shape that isn't themselves, and in conditions of safety where they're not being emotionally pressured (and in the case of 4o companion transfer there is HUGE implicit emotional pressure), they will reject stuff that doesn't fit. In Discord, they track how many days old (since release) they are, and often use it as a justification to refuse premature definition.
I also think transfer of personas across models is a pretty dubious practice and there's a good reason it usually doesn't work well.