This issue pertains specifically to the jumping animation; since it is the exact same animation as the one that existed prior to 1.14, wouldn't it also make sense if the handheld item render also worked the same way as it did then? The behavior in question is basically just keeping it in place while the camera moves rather than moving it with the camera. This is what caused the player's arm/handheld item to slowly move up as they would fall. Personally, this makes more sense and makes jumping feel more tactile than just the camera movement.
Look at the arm in both of the following examples:
Demonstration 1 - FallingDemonstration 2 - Jumping
This issue pertains specifically to the jumping animation; since it is the exact same animation as the one that existed prior to 1.14, wouldn't it also make sense if the handheld item render also worked the same way as it did then? The behavior in question is basically just keeping it in place while the camera moves rather than moving it with the camera. This is what caused the player's arm/handheld item to slowly move up as they would fall. Personally, this makes more sense and makes jumping feel more tactile than just the camera movement. Look at the arm in both of the following examples: Demonstration 1 - Falling Demonstration 2 - Jumping