My interpretation of the presented material that no, difficulty doesn't matter, "available resources" too, "impact" - well, the impact you should strive to is exactly the reduction of the most critical risks.

Using the example from the linked material: surely if you can't swim, learning may be quite difficult.

I work in risk management. What you do is time box for risk assessment where you come up in an hour or so with all kind of risks. Then you tackle things that have high chance of showing up or things that have high impact. Ideally things that have high chance and high impact are priorities.

There are different ways to say similar things so your lexicon really depends on where you've spent your time over the last 5 - 10 years. Product Market Fit (PMF), high leverage activities, and risk assessments all overlap in my mind, it really just depends on the book/blog you read.

PMF is really just a way to say "I de-risked these key areas", right? I think it does the best to encapsulate the idea of getting important things right but it's not the whole puzzle.

After PMF popularized, we had tons of people talking about Product/Channel Fit and Message/Market Fit, etc., since you need acquisition channels to work to fulfill demand and solid messaging to drive demand to begin with. Being lazy with channels is a big risk, IMO as a marketer. It's especially risky for bootstrapped startups to waste time on the wrong channels.

It will be pretty hard to pass on company with a real PMF, irrelevant of anything else.

I don't feel that 99% of what people call PMF really exists. I don't think of AI/Blockchain startups ever had PMF at Series A stage and none of the hardware/bio startups ever do.

Closely related I think are intuition and creativity. You can't always with your conscious mind put words on what you actually know.