My understanding is that the fully composted solid waste can be spread on the ground, as it is now soil/fertilizer. If it is not fully composted yet, you can put it in a plastic bag and put it in any dumpster. I don't think you ever would try putting the solid down a toilet...imagine trying to flush soil..?
The liquid on the other hand looks to be very clean. The typical holding tanks I've seen are only like 2 gallons. Dumping 2 gallons in an easy-to-handle container of only liquid into a toilet should be easy and hard to make a mess of.
Cassette toilets on the other hand, I can completely understand your reservation to not wanting people dumping those in your toilets. However, with enough practice and care, it is also quite clean.