A dying entity's hit and collision boxes will still exist in their proceeding death animations, capable of pushing the player and blocking attacks directed towards entities behind the animation.
Tested in creative and survival mode, with zombies and villagers killed by the player. Additional testing by @unknown on Samsung Galaxy S4 (Android 5.0.1).
Linked issues
is duplicated by 9
relates to 4
Comments 11
Too. Not sure this is a duplicate. And this bug is kinda creepy to me when this happens.
Please respond and add the current version if you can reproduce this issue.

Confirmed to affect 1.0.2.
Confirmed in Version 1.0.2 Plus if the player keeps hitting the mob after death the death sound will play multiple times along with the sword swing sound also if the mob does proximity damage (slime and magma cube) the player will take damage if they step in the hit box during the death animation.
Cleaning up old tickets: This ticket has not been updated recently (~1 year+) so is being closed as Cannot Reproduce. If you feel this is still a valid issue then please comment, or create a new ticket following the Issue Guidelines.
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I'm still experiencing this issue in v1.12.0; I can hit an entity a second time during its death animation. Not sure if that's related to what this bug report details...

Even though this ticket is resolved as "Cannot Reproduce", it is linked in the fixes section for the 1.13.0.9 Beta changelog.
I can still push the entities. So not fixed.

Apparently the fix was made for hitboxes in distinction from collision boxes. However, the changelog mentioned by OcelotOnesie states that both hitboxes and collision boxes were to be removed. So, I have created MCPE-162048 for the continuing issue with collision boxes.
Comfirm on iPad 4 and iPhone 5