Not related to your actual point, but I researched corporate boards a few years back and found many instances of people on boards of two direct competitors. In fact, I found a couple of companies with CEOs who also served on the board of a competitor. This was going through maybe a few hundred large corporations, so I’d have to assume it’s incredibly common.
I haven't studied this in depth but I recall that there's a book out there that sort of blasts the management consulting industry. How a lot of corporates will hire the same consulting company such as McKinsey to learn what their competitors are planning/how they are performing. IIRC
This is absolutely incorrect. Consulting companies, at least the major ones, will never let any consultant work for more than one competitor throughout their career. They also strictly forbid sharing any info learnt about a company with anyone else, talk less of with competitors.
Eric Schmidt sat on Apple's board while running Google, but left in 2009 when they became competitors in the smart phone business. Before that, Apple & Google weren't competitors.
This is notoriously playing out in the ETF space. Large institutions own vast quantities in stock in competitors and competition decreases as a result. See Rise of Institutional Investors Raises Questions of Collusion.