Several times already I’ve matched 3 TU tiles to have my total go up by only 2. This usually happens when the teamups are matched as a part of a cascade, or at least an initial double-match (where I match 3 TUs and 3 colored tiles at the same time.)
Is this a known issue?
It’s a feature. 
But seriously, it’s normal. Cascades reduce the amount of TU AP, as it did for environmental tiles.
I’ve never noticed that before. I just had a cascade match 2x3 TUs, and only got 2 AP for it! Why the hell is it this way?
The AP gained for TU matches is subject to the cascade penalty.
How exactly does cascade penalty work, and does it affect anything except TUs?
IIRC it’s 25% less each extra match, and yes, it effects tile match damage too