Two things - are you asking about the double-sided lever or the clamp-on brake caliper as well?
I’ve used one of the levers, it was pointless, but I haven’t ever used the clamp-on brake. ( it came with round fork bands instead of oval). It looks ok but the bands will mess up the paint on your forks pretty easily.
I think the “sub-braking” description comes mostly from both the less-strong-than-usual attachment of the caliper, but also applies if you use the short side of the lever, since the actual leverage is a bit poor.
The lever has some design issues. If you install it as intended, you end up with a short lever on one side, that takes a whole lot of force to work with one finger, and on the other side the longer lever is mostly inaccessible, being in front of the head stem. In other words whichever side you use, your hand must be almost up against the stem - not the best place for your hands if you’re using it in an emergency. Also, you inevitably end up with the brake cable running straight out where your hands would usually be on the tops of the drops.
I ended up switching it upside down, so I had one longer usable side and one pointless short side in front of the stem. Pointless. So I took it off and replaced it with a bmx-style one, similar to a Goldfinger.
as for polo, i think the best setup is to ride fixed, with a really low ratio, so you never need a brake anyway. with a 2:1 ratio you can usually skid without even getting out of the saddle, and you can think about hitting the ball instead of hitting the brakes. i run 39/20 and it works a treat.