I find that quite often, gut-feeling turns out to be more useful than a list of statistics (Not to take anything away from Vaya³'s post, it's still very interesting). Because as you say, you're only as good as your last performance and every rider is on another point in their career (or season, even).
I do believe that Pogacar firing on all cylinders in the classics shouldn't hamper him come the Tour. The human body recuperates. And there's a lot of time between spring and the Tour, in my opinion there's no reason he shouldn't be back at 100% in july. We're in for a treat it seems..
To the bolded, to me that's the 1 million dollar question. But is it true? I mean the kind of effort it takes in today's cycling to do well in both Flanders (not to mention a full tilt already at Strade Bianche-MSR, with TA in between) and then the Ardennes classics (at least LBL), and then again get ready for the Tour o-p-t-i-m-a-l-l-y is formidable. Not since the 80s has this kind of campaign really been done; when, as Fignon said in his book, the last generation of romantics adventured throughout the season. That is, before the mounted data computers/race radio/tech regime et al took over. Hence, as the general level rose in the peloton, riders had to pick and choose their targets, because the performance science has made it well-nigh impossible to be good enough in a nearly full classics campaign and the Tour in one year.
Now Vingeggard isn't doing the monuments. Instead, he is patiently building his form with every effort/rest period in full function of the Tour and only the Tour. In theory, therefore, the Dane will arrive at the Tour o-p-t-i-m-a-l-l-y prepared, not having "wasted" a single pedal stroke on anything that wasn't in reference to the Tour. This has been the standard way of doing things to win the Yellow Jersey for several decades now. By contrast, Pog is disregarding this model. He audaciouslly throws caution to the wind and sees opportunity to win big on every front, so doesn't hold back. Bravo, but this could also indicate an exceptional all-rounder knowing his talents have a limit at the Tour, extremely high though they doubtless are. So why deprive onself of a Flanders' victory, when you would gain little, if anything, at the Tour by skipping it? Maybe Pogacar being so good at so many things, means he can't reach the same ceiling as Vingeggard for the one-thing Tour.
This is to say, Jonas may be so good that come July perhaps Tadej will meet his match (again). This is my suspicion anyway. Interestingly, Cancellara has recently suggested that Pogacar has now become more of a classics rider than a GT specialist. Now at first this may sound crazy, the statement of a former rider who has just become a bit silly, but that on futher consideration may actually have a certain logic (at least when compared to Vingeggard).