Alternator, 'Clutch' Pulley - Confirmation Required - 2008 335i, N54

[Codes2]

Hi All,
I've googled for a long time on this and not found anything definitive.

Does the Pulley on this alternator actually come with a 1 way CLUTCH?
Has anyone put their hands on their own Alternator and Pulley and spun the Clutch?

Mine is fixed solid on the shaft, and has zero play. Possibly defective...
They are commonly called a Clutch Pulley, however I am not reading anything beyond the name that suggests there is a Clutch.

I have a hard time to think how a Clutch would be necessary... maybe letting off the gas quickly where RPM would drop fast? (but really?)

I'm working on this part of my car now, and want to replace ONLY if necessary.

Thanks!!

My original model PN 0121715016

[Codes2]

Well, I've had confirmation on another forum.
So, I've ordered an entire Alternator w/ Pulley.
I'll post my observations here following receipt.