How is Mercy "fine" debunking Mercy myths

Then I don’t understand what frequency of usage is having to do with being able to do multiple things at the same time. He made a bad case since most other supports can multitask, but this example seems pointless. Mercy couldn’t rez and heal at the same time even if ressurect was on 1 second cooldown, it has nothing to do with ability to multitask or not.