A decline in economic activity :⇔ economic contraction.

You don't have to use the two quarters of negative GDP growth as your criterion, but you do need to find contraction somehow.

The AP helpfully notes you can look for economic declines not only in GDP (i.e. output), but also in income or "other measures."

Output and income aren't quite semantic equivalents (though in theory they're equal).

It's not clear what they mean by "other measures" but I think it's safe to assume they mean "whatever numbers we need to gin up once we get called out on this steaming load."

In suggesting that the economy can fall into recession (and presumably, by their gauge, already has) without ever receding, the AP hasn't just moved the goalposts. They've picked up the ball, declared a new score, and gone home.