Advanced plugins like Bunny Hop Abilities or Super Bunny Hopper explicitly remove this slowdown.

This "no-skill-required" mode is excellent for beginners who want to practice their air-strafing (moving the mouse and keys in sync to gain speed) without being penalized for missed jump timings. 3. Server-Side Reliability vs. Client Scripts

Bunny Hop Enabler (remove the slow down after jumping in CS)