Exactly this.
As a person who does both writer and artist , both specialities require a lot of hard work and effort. I'd never say one is better than the other.
However, at the same time, I understand why this thread was made. It also depends on the level you're at and the amount of work you've done, hence it's not always gonna be 50/50.
A lot of these collabs we see asking for 50/50 do not even have notes or chapters made, let alone finished scripts/novels, to show their skillset. They're not showing people what they're capable of but expect others to showcase their abilities.
For me, it's really based on trust. I need to trust that the person I'm working with can have a strong work ethics and they have to trust that in me as well.
I'm not even counting ones that ask for partnerships because they're asking for someone to write the story with them, not for them.