You're making a mistake Sam talked about in his lecture: measuring a company by the number of employees. Software scales in a way that other businesses do not. Instagram got millions of downloads and a $1B acquisition with 13 employees.
You are correct. I thought about that and was tempted to admit this possibility and not call every business with 15 employees "small", but I wanted to keep the wording simple!
I'm not completely wrong! Commonly many people will regard any business, whatever the revenue or acquisition value, with 15 or fewer employees as "small". They just will!
And there is the recent A16Z essay that indicates that we may soon see a startup, with a solo founder, worth $1 billion. So, such an example would agree with your point.
But such an example would conflict with Altmam's lecture where he is really down on solo founders!
There is an example of a successful solo founder: As I recall, early on the Canadian romantic matchmaking site Plenty of Fish was just one person, the founder, two old Dell computers, ads just via Google, and $10 million in annual revenue.
So, let's, see: Since the business was growing, maybe we should assign a P/E of 100? Since likely ballpark $9 million was annual (pre-tax) profit, maybe for the worth of the business we should multiply by 100 and get $900 million, ballpark $1 billion, from one person! A "small" business? Maybe not!
Yes, what Altman was talking about was a venture funded business with some explosive growth potential, but, still, when the company had just 2-3 people and was on the way to 15, trying not to hire, maybe not yet profitable, their value unknown except for the terms of the VC investment, maybe they are still a "small business".
Maybe a point would be that what Altman was talking about is so desperate to achieve the explosive growth potential that the office likely necessarily has a desperate air where one bad hire could wreck the company. Still, the strong conflict with so many millions of US small businesses is tough to swallow.