Driver CV Axle Machining Grooves

[83Daytona]

Just replaced my CV’s on my 2013 1.4L 6MT. The OEM CV axle on the driver side had some machined spiral groves on the neck of the spline shaft end that goes into the transmission. The aftermarket CV axle i got (Rockauto) did not. Length and other design features were the same - I installed it no problem (except 1 concern see below). Any idea what those machined grooves are for? And do i need them? (Stock google photo of the machined splines below)

Additionally - while I haven’t driven the car yet (waiting to get some MTF from the store today), Does this driver CV look fully seated at the transmission? It popped in nice and I gave it a few inward “pushes” , but I still have that nagging “what if” in my head. Will i know right away if its not seated if it leaks? (Second two photos are my car driver CV at transmission).

 

[83Daytona]

Update 12/28/2024 - Drove the car around town a bunch today - No leaks as of yet - No strange noises or anything like that. So I think I'm good - The only thing hanging out there is I could only find 2 quarts of Amsoil MTF in town so I drained and filled the MT6 with 2 quarts. It looks like most people are saying to use 2.25 or 2.5 so ill snag another quart somewhere else. Ill probably use Redline MT90 if I can find it.