Begs the question how big the improvement was precisely
Bernal's? That is a good question -- I'd say noticeable if not huge, and he benefits from being on Ineos vs., say FdJ...
We'll never know, although in 18 he was as strong as he needed to be -- and before the TdF last year he had big results in ToC, Colombia and Romandie, and won the Colombia ITT title. This year he upped his game with Paris-Nice, Suisse and Catalunya before the Tour. If he wins Lombardia or is very close, I think we can agree that he's got a lot of headroom in his career rather than just being a stage racer.
I actually think Pinot has made a real, and surprising, leap since 2017, despite the Giro disaster. At the end of last year he was as strong as anyone and his Italian campaign was unreal.
I've said this before but I think we're in something of a golden age as far as GT contenders. I think the Vuelta was a bit of a dud, but there are about a dozen riders who you can realistically peg as podium favorites in any given GT, either now or in the next 2 years -- and I'm not including guys like Bardet, Majka, Chaves, Aru and Mas, who seem to have taken backward steps but could rise from the semi-dead.