The 'Lean Startup Methodology' is a management fad like any other. It combines obvious advice ("don't waste money", "avoid wishful thinking") with a large dose of folklore.

I run a website that didn't make any money for four years, then unexpectedly took off. If I had been 'ready to pivot' after the initial failure, I would still be broke right now, and I would have no idea that I had even missed an opportunity.

That doesn't mean that 'lean startup' principles are wrong. But they may not be all that right, either. I would urge people to make their own mistakes, and draw their own lessons, rather than listening to too much received wisdom, particularly when it comes from people whose livelihood depends on sounding like they know what they're talking about.