Please expand on this. I am not following.
The constitution states that the power to appoint "Officers of the United States" (which is what any of these commissioners on an executive branch commission would be) rests with the President with the consent of the Senate. The same article allows the Congress to vest by Law the appointment power (1) to the president alone (i.e. not subject to Senate consent), (2) to the courts of law, or (3) to the Heads of Departments. These are the three choices available. If the congress decides to pass a law vesting in itself the power to appoint the commissioners then the congress has unilaterally granted itself a power that is outside of its authority under the constitution. The constitution was specific in what it granted to the congress regarding vesting the authority to appoint these commissioners and the congress ignored the rules and passed a law granting itself a power it was not constitutionally authorized to grant. What part of this is too hard to follow?