The "trusted source" is the office of Rick Smith. It's a deliberate leak intended to send a message to the Browns that they shouldn't bet on Manziel making it past #1.
If we want Manziel at 1-1 we believe he is a franchise QB. What could Cleveland possibly offer a franchise a franchise QB away from a Championship? No, what this message does is put Clowney in play for the #2 slot.
If I'm a franchise who wanted Clowney, I now "know" he will be available at the #2 pick because Houston is going to take one of those two QBs. So I'm going to make a deal with the Rams to get Clowney.
If I'm Cleveland I'll make a deal for the #2 pick if Manziel is still there. If he isn't, I'll stay in my slot & execute plan B.
The only way I'd consider trading with Houston to get Manziel, is if I believed St. Louis or Jacksonville wanted him.