No, no, no, no. This is exactly the kind of thing a business guy would use to make what should be an exercise in research and negotiation into seeming like it's "scientific". Bullshit. Research and negotiate for what you're worth. This is the biggest mistake I see technical people make with businesspeople - ask for more, don't be meek and buy the business-guy "this is how it is" BS with unnecessary totally subjective fancy charts. And I say this all as a business guy, by the way.

Edit: Here's how I'd reply: "That's a great chart, it makes total sense to me, I can see how you'd come up with the 20% number... just from the research I've done on how much exits are usually worth, I'd be looking for something around 30% to come onboard, and I'd expect to work my ass off to be worth that. I'm making pretty good salary right now, but I am really excited about this project - how can we make this work? What would you expect out of me for me to be worth 30% vesting over XYZ timeline?"

In other words, don't argue, indicate you've done some research, don't trip the other guy's ego defense mechanism, state what you want simply without grandstanding, focus on delivering value, and then ask what you'd have to do to be worth that. It'll work. Really, unless they were offering something overly fair to begin with to be cool, a businessperson will respect you more if you negotiate with them a bit. Makes you seem like you've got a spine.