Welcome to thee forums. I don't know much about Gios but they did make entry level models with hi-tensile steel, so there's no reason to believe they didn't make an Aelle model, though I haven't seen one. Still, as you state, Aelle typically used a 26.8mm post, while 27.2mm is typical of SL. It's always possible that the seat tube had some aggressive reaming, so to increase my confidence I'd be checking the steerer tube. Aelle did not use the Columbus steerer and therefore would not have the dove logo on the outside or the five helical ridges on the inside, at the bottom. Of course, this still isn't infallible, as the fork may have been switched.

Your bicycle appears to have recessed brake mounting, so I wouldn't think it would be pre-1979. Campagnolo catalogue 17a (for 1978 model year) doesn't mention this option for the brakes and the 1977 Gios catalogue shows exposed brake mounts. Regarding brake cable tunnels, the 1981 Gios catalogue still shows them. Of course, that assumes this is a legitimate Gios. It's my understanding that they are a commonly faked brand.