Signing McDaniels directly also helps the Rockets. Had McDaniels signed an offer sheet and the Rockets matched, they would not have been able to trade him without his consent for a year. Going this route, McDaniels is more valuable as a trade asset to the Rockets.
That may be significant considering how McDaniels didn’t play much at all for the Rockets last season and, on paper, he would seem to be behind even another three in rookie Sam Dekker. McDaniels showed some real value in Philly last season as he has some insane athleticism and defensive potential, but needs to work on his shooting (28.7% from three last year).