I think I would take issue with this thought. The idea behind grooving is to drain water from what otherwise would be a flooded runway surface. Wet and flooded runways probably need to be viewed quite differently from the point of performance calculations ?
Surely without drainage the runway would have standing water which will affect landing distance. But pilot calculates landing distance by reported Runway Condition Code. That's provided by ATC. Pilot has no means to use the information about grooved or ungrooved for altering the LDR. May be ATC uses that information to designate the code. Pilot only uses the code. That's why MM said it won't matter.