You were right, the BKOOL Pro actually has power meter built in. If I use that instead the resistance control works. However, the resistance is waaay to much, I get 40 cadence at 0-3% slope which isn't real. Tried lowering traniner difficulty in "Settings" all way down to "Off" but doesn't seem to help. Also, the built-in watt calculator isn't very accurate vs the 2-3 times more expensive external power meter so I'll stick with power meter until I can use that with resistance control. Hopefully just a software bug in Zwift maybe.
Being pedantic ... I don't believe the bkool pro has a real power meter built in, rather it estimates power from the speed of the roller and the resistance it assumes is being applied in response to the resistance setting the software has requested of it. The actual exact resistance applied is not known, as it depends on calibration, temperature, tolerances, electro magnetic efficiency, etc, so the power estimate can be rather rough!
A power meter would attempt to actually measure the power being produced, whereas I understand that the bkool uses software to calculate a rough estimate of the power. It may then report this power calculation over the ANT+ profile, but it could hardly be referred to as a power meter, except in the loosest sense.
I checked my bkool pro with a powertap hub and saw variations in power reported of as much as 30%. The powertap has been checked with the power meter in a KICKR and variations are only a few percentage, as would be expected with any true power meter.
If the bkool did have a real power meter built in it would be considerably more expensive, and hopefully more accurate!
Geoff