This is pretty damning. I can think of no other reason to do this other than to help out the Democratic nominee.
Bill Clinton initially said that Hillary “frequently” passes out, then said he didn’t mean it. CBS decided to accept his explanation by deleting the whole moment. Because Bill Clinton would never try to deceive anyone.
I’d note that this is no random, isolated mistake. Several people in the newsroom, including Charlie Rose must have noticed that Clinton had said “frequently,” since it was a significant comment, and must have seen that it was edited out.