I didn't read that as "if you have $1M you'll almost certainly go to $2M", so much as "if your business has already earned $1M in profit then it's almost certain to continue to earn another $1M in profit". And likewise, it's not talking about having $1M in savings from a lifetime of hard work.

Think of a business as being like an engine. Until you get the engine started and running under its own power, it's just costing you time and effort and money. Once it's running, it generates money at an accelerating rate. The $1M cutoff here is a proxy for "the engine is running."