Steve and Alex are not using their updated skins whilst the game is offline

Steve and Alex are using their old skins when in offline mode.

This can be reproduced by logging into the game offline or by logging in with an invalid user.
This can be fixed by updating the following files in the resource pack:

/assets/minecraft/entity/alex.png
/assets/minecraft/entity/steve.png

Attached is a screenshot of an invalid user logged into Minecraft Java Snapshot 22w42a. 

Additional Note:
According to the comments on this bug report, these textures also effect the default Player Head.
Attached is a screenshot of a default player head placed in Minecraft Java Snapshot 22w43a.