Unfortunately, I can not answer about CMMI. However, I can answer about ISO 9001. Startups, in reality, are not yet companies, they are still projects of companies in search of a successful business model and customer fit. So, a startup is like an experiment being done. The startup can be called a company only after finding the right business model, a customer fit, and when it starts scaling. Only then, the procedures and internal standards are ready to be documented.