If you read a broad cross section of posts in this forum a pattern emerges. American Express practice frequently diverges from policy, and very often in the customer's favor. I think we can find reported exceptions to every American Express policy.

In this instance I think it's accurate to say that American Express (USA) policy is to limit individuals to four credit cards, but they won't proactively close accounts if you already have more than four, and that it's not impossible to negotiate an exception.