Technically a restart includes a failed guess but who's counting? Get it? Who's counting?
Difficulty score 13. No green.
Restarts are not necessarily guesses. Sometimes a lapse in concentration can result in faulty logic which eventually forces a restart. That is especially true of expert puzzles when using a forcing chain, faulty logic at any step in the chain can lead to false results and eventuate in a restart.
Or put another way, you may be applying correct logic, but just get tripped up in the mechanics of it. It's like making a mistake in an arithmetic problem, you were not guessing, but you did make a mistake.