I'm pretty sure it is what I stated above, where if an RFA signs late, the team gets charged the salary for the full year, rather than the partial year they played for. This would have been instituted to get rid of loop holes where a team could make a player sit out to get cap relief.
And if this is what he means, then it isn't a blanket 30k per day. The amount is based on what the player ends up signs for, and if the player doesn't sign, then there would be no cap hit at all.
Though I can't find that documented anywhere either ... but that makes more sense to me then penalising a team with a cap hit for an RFA sitting out.