Since this is primarily a technical analysis site (right?)

In the posting text, the author emphasizes that the current wave 3 MUST make a new ATH, AND the subsequent 4 down MUST overlap the wave 1 high for the ending diagonal pattern to play out.

Technical note … EW folks are usually aware that the peak RSI in a structure will be associated with the 3rd wave within the larger 3rd wave. The lower degree third is not labeled, but can be easily seen at the Jan 2018 point.