That's essentially what the GP was implying, "Have everything in writing, complete with date and signatures."

Nowhere were contracts mentioned. A proper proposal, for example, always has a date and to sign it if agreed to is just professional conduct. I’d be wary of any exec not willing to do that. Instant red flag.

That’s what a proposal is too, it’s not necessarily a demand

That's fair. I've worked at more established places with formal design doc/RFC and sign off processes and it can work well.

After reading the description of the SOP at this shop, the idea that the OP would be able to introduce an additional layer of process requiring multiple stakeholders and management seemed like a bridge too far in my mind :).