May be you were watching something else.....
Or maybe I wasn't letting my prejudgment of Team Evil cloud my view of the racing? I've just googled for some numbers to see if they bear any relation to what I think I saw...
According to the internet armchair experts, Aru's estimated average power on the final climb was 5.7w/kg. Impressive but not superhuman.
Average speed for the stage winner was 30.2km/h, which is sloooooow for a GT stage, even one as tough as yesterday.
A couple of riders did stand out as looking a bit fishy to me yesterday. One was LL Sanchez, who seemed to do some very long stints on the front, as well as regularly dropping back to the team car to fetch water bottles. But then he ended up 12 minutes down (even behind Froome) which makes his performance look a bit more realistic. He's still a nobber though.
The other was Valverde, who is going remarkably well considering his season started in January and includes some big spring Classics wins. But then at the tender age of 35, he's just coming into his prime in Vuelta terms. And we all know he's a dirty cheating nobber anyway.