Okay, I'm still a bit confused on a technical detail here. When they annualize the GDP change, is it sequential or annual? They certainly aren't taking the Q1 to Q2 change, applying it to Q2->Q3 and Q3->Q4, and reaching the 52% rate?

It's less of a concern with smaller numbers. If the GDP declined 4% on an annualized basis, you could see that if each quarter declined ~1% quarter-over-quarter for four total quarters, you'd end up with something quite close to 4%. But 52% sequentially is like expecting a 20% drop Q-over-Q for four total quarters. (1 * .8 * .8 * .8 = .512).

That certainly is not true, and not what I learned, but the language I'm reading seems to suggest that.