Clicking fast when hitting mobs results in insane knockback

The issue with using extra durability is already tracked in MCPE-167031.
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MCPE-167031 is not related to hitting fast; losing durability from hitting fast was tracked at MCPE-157150 and reported fixed in 1.19.60.

Confirmed that you can launch a mob up to 3x the baseline sprint + knockback 2 distance by spam-clicking. Auto-clicker is not required.

The behavior described here is a result of two things:

1. You can hit a mob again while it is still in flying through the air from the knockback of the first hit.

2. Hits can deal knockback while a mob has damage immunity. Knockback can be dealt at least once every 4 ticks if not more frequently.

Of these, (2) seems more like a bug to me than (1). If knockback had an immunity period like damage does, then (1) would not be an issue because mobs usually either land or fly out of range of the player's attack within 10 ticks.

These examples show different amounts of knockback being dealt by spam-clicking while sprinting with a knockback 2 sword. A particle command is used to show the husk's server-side trajectory.

Here are images of the full trajectory of each example:

By comparing these, you can where the hits that add extra knockback register. The trajectory speeds up and goes upward slightly.

Can still reproduce in 1.21.101. In this video, I attack the first Husk by clicking once, and attack the second husk by spam clicking. The spam-clicked Husk flies much farther.