I don't think it's hard enough for a break to not succeed. There's nothing for sprinter teams to chase for (unlike Friday, when Bora and Quickstep will be working for Ackerman and Bennett), but there's no benefit whatsoever to Jumbo to chase down any attacks.
The only problem for JV is that with 2 hard-ish mountain stages done and dusted, there isn't a classics rider or a sprinter within 5 minutes of the lead who they could just allow to go up the road and borrow the jersey until the Tourmalet. Anyone still in the top 25 is still a theoretical, potential threat.
Well, there has been a very compressed calendar with very little time for recovery. Riders have gone from an extended period of no racing to several major races in a short period of time so form fluctuations are a lot wilder than we might ordinarily expect.
I get the impression some riders still believe the Vuelta can be a fun little ride with the teammates or a training exercise to get their form back. Honestly, when I read comments from Pinot before the race (i.e. "I want to rediscover the joy of riding etc" or words to that effect), or Guillaume Martin this morning who expressed surprise at the "violence" of the pace on day one, I believe those guys didn't mentally prepare themselves for what the Vuelta really is these days, aka a hard as hell bike race with constant action & stress from minute one.