Not creating gatekeepers is good advice.

The sort of meeting described in the article seems custom-made for gatekeeper creation.

If a meeting is about something else, don't raise your irrelevant idea. If a meeting is about your idea, then why are you having it if you haven't fleshed out your idea and already talked individually with a lot of stakeholders?

The only reason I can see for this sort of behavior is a kind of naivete that ascribes immense valuation to ideas, coupled with fear of losing credit if the idea loses association with your name.