Why not a 21.6mm x 21.6mm sensor?

in the context that he stated "dubious claim that 4:3 is "the ideal ratio" it implied that the people who designed or decided that 4:3 is the ideal format made an "unreliable" (i.e. other meaning of dubious are untrustworthy or undependable) choice or decision. The claim is in reference to 4:3 format by the person. 4:3 is our topic right? the Academy of Motion Picture Arts made the claim or call that it (4:3) is the ideal ratio format in reference to historical and factual events. So to rephrase his statement... Designers and people (including me) involved from 1920s to current year made unreliable or undependable claim that 4:3 format is the "ideal ratio.." what else is the dubious claim? the 4:3 format. Even if you refer to the person as the "dubious"... that still implies the 4:3 format is unreliable because the person who selected it was unreliable or untrustworthy.