I suspect they were thinking of a USPS "hold" (where they keep your mail at the post office for 30 days). As you said, a change of address costs $1 (online, free in-branch) and lasts for 6 months with the ability to extend it for an additional 6 months after that (up to 12 months total).

Oh, you're right! And they also don't forward 'spam'! My mistake.