I have a couple of takes... including on Randy's point:
1) I see a lot of veterans that get moved for a pick returning really, only 6th's or 7th's. Maybe Brad is stocking up on some of these late rounders in anticipation of this? He's not looking to trade 1sts or 2nds for a star, but rather, 6th's or 7th's to pick up a depth player to cover for an injury, or similar...? Just a guess.
2) My other take is: Not only is it getting really hard for 3/4/5th's to make this team... but ALSO: if you release them at the end of training camp it's harder to slip them over to the Practice Squad. And Holmes especially is going to have a hard time slipping those picks to the PS because it's getting known around the league that he's a pretty good judge of football players. HOWEVER... those 6th and 7th rounders are all projects. Long shots. Practice Squad players. Maybe Holmes is INTENTIONALLY stocking up on 6ths and 7ths, both for future trades, but also because he may have his eyes on several guys that he wants to draft and develop, and those guys will all be in the last two rounds and are easier to slip onto the Practice Squad without other teams' raiding his guys.
That's my conspiracy theory anyways...