I do not believe smaller than 170 mm. cranks are "overrated".

Some people use them because longer cranks give them knee pain. If a rider has no knee pain, & tries shorter cranks, with no great difference, then they may consider such "overrated".

Recumbent riders in particular seem to find shorter cranks better.

I don't have the URL's to hand, but can probably find them if requested, which highlight measured rider power output improvement with shorter cranks.