I think all the window seats of exit rows 31 and 50 on 77W do not have windows. You can turn your head around when your seat is fully reclined and view out from the window behind you. For that reason, I always avoid exit row on 777 flights across the Pacific. For 767, I think some rows in the forward economy class cabin do not have windows at all or the are misaligned, row 13 is for sure one of those. I am not sure about other rows in that section.