I believe (not 100% sure) that DC owns the production team that covers F1 for C4, so he may be in a deliberate 'role' with them.
C4 also seem to get good access to Red Bull, like Horner speaking live a few times each GP, before during and after.
I think it works, but I understand that if people follow other teams it can be biased, but try as they might, there is never going to be unbiased commentary
The teams that interact with the broadcasters are always going to have the opportunity to present their view. I dont think any teams are excluded, but there is only so much air time