It's true and October 20th is exactly why you got burned.
The mechanic is simple: a new pin takes weeks to accumulate enough engagement signal to surface reliably in search. If your pin needs 6-10 weeks to warm up and you want it hot on December 1st, you back up and land on mid-September at the absolute latest. Late August just gives you buffer.
What I do now: the guides themselves go live end of August with last year's evergreen framing. Then I add fresh images to the same URLs every couple of weeks through October. By the time the December searches hit, the URL already has history and the new images inherit it instead of starting cold. That single change moved my Q4 from "ramping up as it ended" to "peaking December 3rd".
And yes, it feels deranged to write about Christmas in August. You get used to it.