I think both dj's who only play techno and dj's who mix it are both valid approaches.
Its just a style thing and this is some dj's style and they are good at it and can get away with it while some dj's i would prefer to hear play techno all night because this is what they play best. Neither is wrong, and really i can enjoy both just depending on what i feel like. I think the important thing is going to see a DJ's interpretation of the music and as long as its done tastefully and i'm in the mood for it then fine by me. Also techno doesn't haven't to be all 4/4 tyranny, there does exist techno without 4/4 beats. One more spanner in the works here-maybe peoples interpretation of dance music and or techno can differ from their exposure depending on their age and locality so its going to be impossible to come to a general consensus. Its all good if its good. Quest