I don't get these difficulty ratings either. The first of these puzzles was unsolvable (completly illogical) with a three star difficulty, and this one has five stars while being completly logical and not very hard...
The qualification of the difficulty is an old issue, it seems that we are enough to think that the system, probably automatic, does not have much success. As for the first puzzle of the series is unsolvable... there are, for the moment, 56 cases that deny it. There are those who think that are logical all those who can be solved by observing the lines separately and those who consider it because they only have one solution, even if it is difficult to find; both have their reasons. I regret that this is one of the second type, but I have not been able to improve it.