Early startups at the end of XX century adopted engineering procedures similar to those of big companies: long development cycles, product launches, detailed business plans, goals, etc.
This business school approach ended in failure almost always. Losers blindly execute a rigid product management and introduction methodology, trusting everything to the vision and the funding.
Successful product management happens when one team reports to one leader. That leader manages the information loop from customers back to product development, and back out to customers in a continuous flow.