Yep same here - the uppers on both pairs of SIDIs I own are synthetic. Both breathe well enough that even riding in FL summer, my feet don't bake (or at least, the rest of my heat discomfort outweighs any potential foot discomfort
). The synthetic leather on the T2 does a good job at wrapping the foot. The 'Italian microfibre' on the Ergo, that does a bit of the 'bend and fold' thing above the ball of the foot. Going to see if I can get a pic up to illustrate.
(edit - nope still can't post pics, even from my own device, until I've made 10 posts...)