...thought I'd finally check out the PNW forum...
Beko knows his stuff. You can easily do this on a touring bike with 32's. A friend brought his 520 on the JWT a couple years ago, fully loaded for a dress rehearsal just for grins. I brought my old school rigid MTB with 1.5" Armadillos city tires and similarly loaded down. No problems. Everyone else showed up with an assortment of mid to hi-end MTB's. Way overkill.
Just to be clear, I think the conversation is about whether you could get over the Naches Trail with a bike using 32's. (not the Iron Horse Trail).
If you go back to the link above showing guys crossing it with 4x4's, the pics show some pretty extreme roads. I think the issue was raised because the photos show a fair amount of mud. It's also not clear to me that in the 4x4 adventure that they actually ever made it *over* the pass.