That's actually pretty brilliant. Send a couple of regular cruise missiles at ordinary targets and have a couple of MiG-31s loitering within striking distance. Either the Ukrainians launch and expose their positions to quick Kinzhal counter, or do nothing, and lose whatever the cruise missiles are targeting.
Russians might just as well send MiG-31s into Ukrainian radar range any time anything gets launched, just to mess with their heads - "Will they? Won't they?"
This was brough up in this thread and in one of the many articles about why Ukraine needs to be given NATO Gundams to fight Russia. Limited resources and depletion of the soviet stockpiles forces Ukraine into a position of either hitting anything that enters at the expense of existing stocks or having to prioritize and trying to figure out what is a decoy and what isn't, with the corresponding risk of letting something real through.