I've never run into anyone who's defined it the way you do; everyone I've heard define it does it in terms of not yet having taken a cash investment from a non-founder.

"We've bootstrapped the company so far, but we don't think we will ship a MVP without taking at least a seed round" wouldn't draw any protests of misuse, in my experience.

You are correct that most bootstrapped companies that have launched end up supporting themselves; that's survivor bias in action.

I'm more used to three previous definition. I would say those companies have tried to bootstrap, but bit successfully achieved it. Of you are a successfully bootstrapped business, you achieved goals without taking outside investment money.