It seems you're right.
The PLi team removed the whitelist option.

https://github.com/OpenPLi/enigma2/blob/master/lib/python/Components/ParentalControl.py

If the /etc/enigma2/whitelist file exists it will be threated the same as the blacklist.

I only use the parental option based on EPG info.
If a program contains the 18+ tag it'll ask for a pin.