If he did one last big pull (which was hard anyway in a descent with some rolling parts), he would have been dropped before the finish.If he actually had emptied himself completely he wouldn't have been able to stay with that group until the end. He could have pulled until he didn't have anything left like you see during the TDF where guys like Gesink empty themselves until they can barely spin the pedals anymore. That's what "empty" looks like.
It would have been better to do one last big pull until he had nothing in the tank instead of holding on and doing these weak pulls.
Now step into Roglic's shoes and think about how you would feel if you just sacrificed your country's chances for a podium or win by dropping out of the chasing group at the very last part of the race, having to explain this on Slovenian TV and in front of your team mates?
Get real I would say.