Weird cutting tool.

[Shootymacshootface]

Sometimes reamers are made with flutes like that to avoid hogging in, and made spiral so that they can be used in holes with keyways or other slots, etc.

If that is an endmill, other benefits would be that it would push the burr down instead of pulling it up. Also, if you are cutting a fragile material that is prone to chipping you would use a sacrificial backer, the endmill would push the material down into the backer, instead of lifting it up off of the backer.

 

[Flyinfool]

That is a right hand cut left hand spiral chucking reamer.
Here is an explanation of uses for left, right, and straight flute reamers.

Reaming with Left Hand Spiral Flutes vs. Right Hand Spiral Flutes vs. Straight Flutes « Super Tool – Precision Cutting Tool Manufacturer