I think it's that size that is problematic. Something just a bit bigger than a wide country technical friend #6 (the big green more or less the size of your head). It is problematic for me as well, that's how I found the forum thread. It is not that it's undoable to climb this with the 'caterpillar' technique:
- press inside of your knees on one wall, heel on the other
- squeeze a bit
- lock the torso and hands by either chicken wing (if possible), arm bar or putting your hands in front of you and pressing them hard to have a spinal cord - breast - forearm lock
However, I find this technique very strenuous and I get exhausted after 1.5 m or so. Moreover it feels very insecure. The moment I try to relax, is when my body is just a few millimeters smaller than the crack and I feel like falling out. Constantly applying the pressure with the inside of your knee (having the leg a bit like for breaststroke swimming technique) is not a rest position at all. When I am trying to go a bit horizontal, I get an artificial overhang and it spits me out even more. One more thing to keep in mind is that because #6 is just not big enough, I can probably find only one spot to place it somewhere in the crack (usually it's at the beginning of the crack, as when you go up the deeper part usually widens for obvious erosion reasons) and then I have to solo the rest.
I've tried bros where I climb (the pictures are from there), but the rock has just so rough surface, that I cannot get a decent placement with them.
I do agree it's more of a squeeze through chimney rather than the offwidth.