Every pickaxe has to be labeled as a melee weapon in stw, and this is the asset file for the pickaxe in STW
HightowerTapas = Thor Pickaxe
For some unknown reason, the stw team thought it would look better using Thors pickaxe animation rather than what the Other Modes team used for the other mode. This is 100% on purpose, as this is literally the pickaxe file for stw.
Video Example: (credit u/Allanfxxk)