I appreciate that you said repeatedly that, "FOR US", going high fidelity was better.

We have a design system in place and since people know they're not allowed to argue if the text will be orange or blue, there's no reason to go grey.

However, I have had clients that even with the design system in place will keep centering the conversation around colors and font size, when I really need them to tell me if I've got the hierarchy right.

Boils down to: Know your audience and know which tool is going to get the conversation you need.