Even so, it's pretty cheap. If the map is advertised as a guess map, then that's fair enough. But if you go in to a parkour/maze map and then half way through (or even worse) at the end there is a guess, that makes me do this..pol, it is a valid mechanic that has been used successfully in several maps. The main frustration that comes in relation to drah's maps is where he uses it. Having to guess at the very end of a parkour map has frustrated people for a long time. However, as previously stated, other maps that have implemented it as a "main body" mechanic are considered enjoyable.
Just because the way something is implemented in some cases is frustrating doesn't make it invalid.
To me it feels like the map maker is like.. Oh, I need some filler. I know, a pointless guess section