Two For One challenge requires you to have bias_count equal to multi_count.
This challenge essentially only cuts down your maximum bias_count. However, following the bias = multi is required on every multi. In other words, you should never go higher than +01x01, +02x02, +03x03, etc.
Winning the round is very possible because the loss of some biases doesn't really hurt your progression too much, you can still compete for top-10 position on each ladder.