If the accumulation of dirt, mud, and snow was a problem, Michelin would had tested that already, and maybe will either redesign the Tweel with those opening covered, or sell an aftermarket set of plastic covers to prevent the clogging.
I see this type of wheels perfect for EVs because they are lighter and can absorb road shock and noise better than the air-filled radials, in addition to being non-flats. If I had a BEV and could buy the Tweels for it, I will. And I will never get them clogged!