How does 3 tick fishing work?

No, there will be no benefits in this specific scenario.

The general idea is that actions require a set period of time. Fishing is normally 5t worth of time. However, mixing herbs is only 3t worth of time.

What is happening is you do a 3t action, but right at the tick when the results are produced, you change your action from "herb mixing" to "fishing", allowing you to fish at the pace of 3t instead of 5t.

If you were to do this faster, the engine detects you changed your action, and restarts the new action instead of giving you the result. You will actually never fish anything if you were to click faster, because the "production tick" will never take place.