OK, it's a year later. We're up to Horizon 7.8.0, Agent 7.8.0, and Mac Client 5.1.0. Unfortunately, there is still no VMware Virtual Audio (DevTap) or VMware Virtual Microphone (DevTap) options in the SfB Audio Device selection, so bluetooth is still a no-go for Skype for Business.
my current solution:
Airpods connected directly to mac (10.14.6).
on mac running parallels with windows 10 and VMWare Horizon Client 5.1.0. SfB works then fine over AirPods.
I admit this is very ugly solution, but somehow VMWare macOS Dev's are not on the same level as their windows devs.