Section 2.2 is within ARTICLE II - PURPOSES and is as much a rule as Section 2.1: "More specifically, the purposes of the Corporation include, but are not limited to, promotion, protection, and standardization of distributed-digital currency and transactions systems including the Bitcoin system as well as similar and related technologies."
If anything given the "include, but are not limited to" language in 2.1 the text in Section 2.2 restricts the Bitcoin Foundation's activities more than anything else in the bylaws. If the foundation, say, decided to promote a new Bitcoin-QT release that included a PPCoin-style central blockchain checkpoint system it would be very easy to argue that they were violating their own bylaws by doing so; you could even sue the Foundation for doing that if you were a member. (but IANAL)
It is a rule to the foundation, but it cannot be enforced over other community members.