@samsaralotus If you mean the bugs related to the graphics engine update, many of them have been fixed on PSO2 JP.
Switching between PSO2 and NGS has been featured in the JP side marketing at least (the recent puso ni comi episodes about NGS), even if the EN side hasn't mentioned it recently, it's too big a feature to not be available at launch.
Though, what about the clients, PSO2 with the engine update and NGS share the same client. If PSO2 were to not get the engine update, the clients would have to be separate. Having the clients separate only to merge them at a later date would be a complete mess to handle, especially with all the different platforms they need to support (MS Store, Steam, Epic, XBox One).
Then there's the new body/face models, what would happen to a player that changes to the new models for NGS if they were to log in the base PSO2?
Not releasing the engine update with the NGS release just wouldn't make any sense whatsoever, the games are too linked for that not to happen.