Return Serve Counter vs Diesel Returner

[Corbon]

So from what I understand, RSC works in a similar way to Shot Counter, the opponent must hit a flat serve, no top spin or spin and you must return it with a flat shot by yourself in order to make it work. Is that correct?

As for Diesel Returner, all Diesel skills basically have the same description, "more and more efficient/precise". Does this mean that your returns will become more efficient during a game or during an entire set or even match?

[straightcash05]

Diesel Returner makes all of your returns better I think, doesn't feel like it's a progression thing to me.