Both Hammerhead & Garmin have tried to align the options to the 3 distinct types of cycling. This makes sense but only if the map layers meaingfully populate the choice they give. Indeed if I look at some of the off-road areas near me then a significant portion of the tracks are UNKNOWN/NOT SPECIFIED, so I don’t even know how meaningful the DIRT/UNPAVED/GRAVEL options are for me. Maybe it’s different where you are?