It is very common in physics that the same phenomenon can be explained using different concepts. Treating particles hitting a regular structure as diffraction of de Broglie waves gives exactly the same results as the momentum transfer approach the author prefers. In fact, both can be derived from standard quantum mechanics and both are widely used, depending on which is easier in the particular case.

However, scattering particles off objects is only one of many experiments they can be done. For instance, one will have a hard time explaining how atoms work without using some kind of wavefunction description of the electrons. Furthermore, as other commenters have mentioned, there are more sophisticated versions of the double-slit experiment, such as the delayed-choice quantum eraser, where the "quantum weirdness" simply cannot be argued away.

Frankly, it is pretty insulting by the author to assume that physicists intentionally choose the "more complicated" explanation over the "simpler" one.