Decreasing the tire size increases the internal air pressure and ground pressure (a problem if you want to go over dirt), but modern tire construction is up to

Decreasing the tire size increases the internal air pressure and ground pressure (a problem if you want to go over dirt), but modern tire construction is up to the task. Also, grippier rubber is usually a trade-off between tread wear and friction. Though with the price of a Boosted board, I imagine their customers would prefer more grip and a few percent of their purchase price for new tire replacement every couple hundred miles.