How come there is no attempt at an "inter-meshing rotorprop" high-speed helicopter?
If labelled 1 to 3 top to bottom, numbers 2 and 3 in the illustration are identical.

A pair of rotors that are counter-rotating. One set is co-axial, the other set is slightly separated. Aerodynamically (dissymmetry of lift problem), I don't see a difference.

In plan view it looks like this:

(Source)



My guess as to why it was not tried, is because the transmission for concentric shafts is simpler, less bulky, and lighter, compared to that of intermeshing rotors (shown below).

Also, in intermeshing rotors the lift is not completely vertical, which reduces the efficiency (source). High-speed aircraft need to be efficient.

(Source)