That's actually almost exactly the same thing my former boss said (he has a Ph.D).
I think there's a lot of truth to it, but it can also be misleading. A lot of these solo-Ph.D startups just chug along for years at ramen or small-business profitability levels. They work, they provide a nice living for the founder and a few employees, but they don't grow. Whether or not they survive seems to depend on how independent-minded the founders are, because the financial returns are often less than the founders can get elsewhere. Anyone with a Ph.D that has the work ethic to run a startup ought to be worth at least a couple hundred grand a year in industry.
There're a lot of other benefits to having multiple founders besides the "don't give up" aspect. Ideas tend to become better when they're bounced off multiple people, since the dumb parts of the idea get weeded out and the clever parts get amplified. Other people tend to take you more seriously when you can say "we" instead of "I". You learn how to compromise and accept other's input early, which is absolutely crucial once you have employees. You get a stronger company culture, which always seems to evolve out of the interactions between founders.
Actually, you seem a lot like my old boss - both math Ph.Ds with an independent streak, except you're half his age. He was a good guy and very, very smart (finished a Princeton Ph.D in 3 years). But the startup I worked at for 2 years, which is now 8 years old, is still limping along and hasn't taken off. And I really think that if it'd had 2-3 equal founders instead of 1 majority and 2 minority founders, it would've done much, much better.