A CTO should know what's going on in every startup function (deekit.com)

I agree that technical co-founders should be working across all functions. Ultimately, they are co-founders.

IMO there's a difference between being a technical co-founder and a CTO?

Cool to see a CTO taking an interest in marketing. The critical aspect of this is if that input is based on a breadth of learning or just engineer-led thinking. By that I mean taking on marketing problems from a technical viewpoint is not always the best idea.