WD Caviar Green from MyBook (WD20EARX) - WDIDLE3 won't work?

My external hdd enclosure quit working, so I took this drive out of the enclosure and installed it as an internal C: drive instead.
I have heard these WD Green drives have an 8 second head parking issue and I was wondering if this particular drive (WD20EARX) has that problem?
I tried to run WDIDLE3.EXE but it just halts saying “Configure idle3.” (no drives detected). I know it says WDIDLE3.EXE is not for this drive, but other users claim to have successfully used it on their WD20EARX drives.
Someone please enlighten me if WD20EARX has this problem and if it’s for some reason a bad idea to use it as internal hdd (if yes, then why?).
Thanks for reading and also appreciate any input.

WD’s Idle 3 mode is a feature designed to reduce power consumption, in part by positioning the heads in a park position (unloading the heads) and turning off unnecessary electronics, resulting in substantial power savings.

The firmware and internal components of a WD hard drive extracted from a WD external hard drive may not be compatible with the WD IDLE 3 utility since such proceedings (Hard drive extraction) are not warranted or supported by WD. Even if the base model number (WD20EARX) corresponds to a regular 3.5" hard drive, the revision (WD20EARX-0123, WD20EARX-ABCD) may dictate a particular firmware behavior optimized for the unit’s original enclosure.

OK I understand, but can you please confirm if this particular model has the infamous head parking issue that drives like the EARS model etc had? Also, are there any downsides of using EARX as an internal drive?

It may or it may not. The hard drive within an external WD enclosure behaves differently from retail internal hard drives.

How do I find out? Is there any way for me to check?

There’s no safe method to confirm functionality, compatibility and risks since such proceedings (Dismantling an external hard drive) are not warranted or supported by Western Digital.