Intrested in the single founder theory, often creators have such strong visions on how something will work that it drives other co-founders away. Some call it stubbornness I guess.
It comes down to percentages. I think what the author is trying to say (and referencing others) is that your chance of success is lowered by being a single founder vs a team. He references the support network and skill sharing. I would argue that a large additional part of the value of co-founders are that by having to at least convince someone else of your decisions, you avert the true howlers. Similarly, you have someone that validates your priorities (really, assessing another shade of green on the logo vs calling the customer/PR/etc?).