The thing is that he's not even holding out yet. He walked out on the last day of minicamp after the walk through. So, he probably missed an hour or two at the most. This was a pretty minor way to try to put pressure on the front office in a situation where Kamara has no leverage as a 29 year old RB with essentially one year remaining on his contract.
If he doesn't show up for camp then things may change. But, at this point we don't even know what he is asking for or that he will hold out of camp.