I understand why Russia may want to open a new front, or feint, near Kiev, but its not like Wagner could remain hidden. US satellites will easily see them massing troops and equipment.
Just their presence will make the Piano Stooge and his Banderite Azov buddies soil themselves, and keep back units from the Eastern Front.
Massing troops and equipment would be a plus for a feint.
Of course, I read that the Wangers turned over their heavy equipment to the Russian army.