Your thread is misleading. He isn't saying Dak isn't needed to have a good QB, he's saying that unlike Dak's relationship with Garrett, McCarthy doesn't need Dak for money (he already has it), or legacy (he's already won a Super Bowl) or to hold on to his job (he has a new 5 year contract). Herd just said the relationship with Dak isn't currently the same as it was with Garrett and Dak because both guys needed each other, and that now the relationship is more tilted toward Dak needing McCarthy. He also said that could change as the season goes on.
As for McCarthy not calling Dak until a week after he agreed to coach the Cowboys, that's hardly proof of anything. Maybe McCarthy didn't think it was that important, but that's not the only possible explanation. It may also be he felt his first priority was to build his coaching staff, or maybe he felt there was no rush, or maybe he was reluctant to start a communication with a player in a tough contract negotiation, maybe he had the flu or was on vacation. The right explanation isn't always the one most akin to a soap opera.