Performing actions while swapping hotbar slots is inconsistent

(Related to MC-308488 and MC-308509)

When switching hotbar slots and performing actions on the same tick, sometimes the item on the previously selected slot performs the action instead.

This applies to “attribute swapping” in PvP such that when swapping hotbar slots and attacking on the same tick, the damage of the previously selected item/weapon and the properties (such as enchantments, special effects, attributes) of the currently selected item combines.

This also applies to placing different blocks rapidly, shown in the attached videos, where selecting the block and placing it on the same tick no longer consistently places the newly selected block. (See comparison between the intended sequence in pre-release 1 and the actual outcome in pre-release 2).

As well as swapping to ender pearl and using it on the same tick, which does not work anymore.