Yes, the development team of HALion and GA are nearly identical, (check the About windows in both apps or just in GA SE) and Groove Agent is different enough just to completely take up their dev resources.
Sure there are several things to be improved in HALion, but it is very usable in its current form (it got the MIPA 2014 award for best VST instrument), and can produce stunning results.
I think they are simply not allowed to ignore HALion (as they did with old HALion versions), instead they should focus on rapid development - we’ll see