Wiper Arm Spline

[Docwra]

    Hello All,

Striped the Splines for the Drivers side Wiper Arm.

Could be an odd question. 
Does the Act of bolting the Wiper arm down on the input Splined shaft create the grooves?
I have Purchased a New-Old stock wiper arm, possible drivers side, the part number aren't a match, but overall length/ dimensions are spot on.
Except there aren't any splines in the wiper arm hole.

Am i being daft? Should i be carefully bolting it down smug to 'Press' the splines into the new arm?
Ta in Advance.
Doc