The Evolution Witch did not have to give Ves any more speaking time.
She was more than capable of picking up his proposal and flesh it out according to her own ideas.
The fact that she allowed Ves to expound upon his idea showed that she recognized him and valued his voice on this matter.
She did not just do so because she liked him or trusted his judgment.
It was because he was a convenient vessel to formally present this subversive proposal to the public.
If the Evolution Witch unilaterally took charge of this initiative, then the political dynamic around it would change. It would effectively make it look as if she personally attempted to rebel against the Red Association that she had pledged an oath to protect and defend!