I see Yamaha have followed and learnt from PG Music as they now have Audio Styles with RT and RD. It was not Yamaha's idea. It took 50 years for Steinberg to add a simple chord track, when did PG have a chord track. If PG had of sold out Biab to Yamaha it would still be midi and so would their keyboards without PG's ingenuity.
The original idea of the Biab Plugin was to add tracks to your recorded session live or studio this way you already have the chords you are not making songs from scratch, that's what Biab main is for. The Biab Plugin was a lite version without zillions of features and menus with a very high learning curve, there are so many DAW users that were put off by the complexities of Biab.
There are users that have learnt Biab over 500 years and would rather ReWire than a simple basic Plugin.
I don't think the Biab Plugin was designed and marketed for you, but for DAW only users that would not go near the Biab main app because of the complexities mention before, so would not a super complex Plugin put them off.
You are lucky you weren't a Win Beta tester when the plugin was first released, if you thinks it's bad now.
Just give it some time it will get there. Adar works flat out every day improving and fixing issues.