I agree, however if you dig deeper on the site you can obtain a copy of the cardmember agreement which contains the following:

Starwood Gold Preferred Guest Level

You may receive enrollment in the Gold Preferred Guest level of the loyalty program based on your eligible purchases for the calendar year. If your eligible purchases during a calendar year is $30,000 or more, you will be enrolled for 12 months in the Gold Preferred Guest level of the loyalty program.

It will take about 12 to 16 weeks for your enrollment in the Gold Preferred Guest level to become effective.

Only the Basic Cardmember will be enrolled. Your enrollment will expire after 12 months unless your eligible purchases during the next calendar year again qualifies you for enrollment, or you qualify for Gold Preferred Guest status under the loyalty program terms.

You cannot receive enrollment in the Gold Preferred Guest level through this reward program if you are already enrolled at the Gold Preferred Guest level or any higher level.

A calendar year is from January 1 to December 31 regardless of when you open your Card Account.