Do you have one-piece or two-piece boot lugs?
It happens more with the two-piece boot lugs that have a toe piece and a separate heel piece because the peak pressure is higher in those places. The Atomic RaceTech, B-tech, M-tech boots were notorious for this; it happens with some others.
All boots get some in slightly wet snow (snowball snow).
Plug boots get markedly less of it because usually the soles are one-piece heel to toe lug so the peak pressure is less, and the walking 'grip' areas are very rudimentary.
(Believe it or not, the purpose of walking 'grip' areas in snow is to create such clumps, because the friction of snow on snow is so much greater than the friction of plastic on snow)
Do not spray anything on them or you'll likely break your neck walking across icy parking lots.
Your best bet is to find a windshield wiper-type brush and keep it in your backpack.
PS if you're skiing in snowball snow, I'll revisit one of your other threads and repeat the Zardoz recommendation for your -SKI- bases.