Have used/planted seeds and cuttings in rockwool cubes many times in soil, outdoors. Never had an issue with watering them. Used garden sprinkler and the cubes stay airy, moist and not water logged - working exactly as their manufacturer intended. Anyway, even if you do water next to the cube and not directly on it, the cube will still "suck" the water from the surrounding soil, defeating the purpose of not watering it directly. Also, not sure why you are using the volcano looking humidifier; cannabis is not a rainforest plant. Save your money by not running it. You are also creating a major risk for mould and fungus to develop on your leaves and flowers if you continue using it turned way up as in the video clip. The only issue I found when using rockwool cubes in soil is when the seedlings/cuttings are really small and it is windy, as this can actually cause the cubes to act like a wick and draw moisture out of the soil and dehydrate the seedlings/cuttings in the process.
Hope this helps.... Organoman.