Human senses are nortoriously unreliable when it comes to assessing the physical world.W.Pastuch wrote: Hardness is just hardness, the shape of the bite zone is a separate topic.
For example, which horizontal line is the longest?
Answer: they are the same.
A tactile equivalent is briefly touching someone who is blindfolded with heated and chilled pieces of metal. They can't tell the difference.
I'm reasonably certain if a blindfold experiment was conducted where the subject was asked to determine the relative hardness of a group of popsicle-stick-sized pieces of pipe stem material using their teeth, they'd reliably say the thicker it was, the harder it was. (It's probably a survival trait that evolved to help avoid tooth breakage)