Well I was right. Issue itself is not fixed yet, but I now know where it’s going wrong.
That A8 address was the one eluding me. And now it’s getting reported.
So the XIAO DOES see the device. The offending code is here:
in the GAP.cpp file in /Arduino\libraries\ArduinoBLE\src\utility.
The issue is that my device/address doesnt make device->discovered() evaluate to true.
… will update when more info avail.