how is this centralized planning? It’s a corporate decision making operating in a free market to optimize for what majority shareholders want (though the majority of shares are owned by few).

Your parenthetical is how. It's not completely centralized, but it is being decided by a very small number of people.

I think the implied thought (?) is there is a similarity between central planning and oligopoly bandwagoning. To my eye, the causes and dynamics are different enough to warrant bucketing them separately.