Grease grooves are for grease,, and have been for decades. The new PCing method eliminates the need for a grease groove in a cast bullet design.
BUT,, if it's there,, you can't easily coat the bullet w/o PC paint getting into the groove. Just ignore the groove,, and shoot the PCed bullets. Or,, if lubing is your desire,, then fine,, use lube!
The ONLY difference in a bullet w/o a grease lube design vs. one with them,, is how the bullet balances,, POSSIBLY at long distance. When you eliminate the lube ring recess,, and keep the bullet weight the same,, the length of the bullet changes slightly,, and MAY shift the balance point in the bullet. Only by shooting both in a specific gun at LONG range,, (200 yds,, or at least 100 yds minimum,) will you determine if there is a difference.
I'm seeing a lot of cast & coated bullets used in USPSA competition w/o grease lubes. At the distances we shoot,, I doubt anybody can find any differences in them.