They said they had no intention of hindering or invalidating ‘legal’ 3rd party docks, where ‘legal’ could be interpreted as “authorized by Nintendo”, which could mean they have every intention of hindering every dock they don’t approve of or get a cut of sales of.

So not “on purpose”

Inventing and implementing non-standard protocol messages to initiate the display is 100% on purpose. It would be easier to just source an off the shelf board and merely design casing around it.

Plausible deniability.