Looking at the video of it, the V-BAT appears to have a fixed pitch propeller for simplicity, directly driven by the a small 2-stroke drone engine.
Two issues with counter-rotating props:
- You now have to have a gearbox for the propellers to drive two concentric propeller shafts in opposite directions. Quite a bit of added weight and complexity. Which means you'll need a bigger engine to boot. And away you go on the weight/complexity design merry-go-round (added weight > more power needed > more fuel because of the thirstier engine > oops more power needed because of extra fuel > oops need to make the prop gearbox heavier > oops need more power > oops need more fuel... you get the idea).
- Stacking two propellers close together is very inefficient, if the propellers are fixed pitch, because the downwind propeller has to work in its sister's wake all the time, with the flow conditions always changing. It'll have to be set at a different pitch, and even then it'll never make as much thrust as the one above it. And you'll STILL have to use anti-torque vanes for precise control, so you're not really eliminating that mechanism.
So much easier, simpler, lighter, to use anti-torque vanes large enough to counter the torque of the single propeller, for a machine that's kind of quasi-disposable anyway.