I notice an update to the Best Practices page:
But there's a bad bit of advice there:
When designing your artwork, create the files at 100% of the print dimensions at 72 DPI. This will ensure a sharp image that isn't blurry or pixelated.
This is wrong, you want them at 300 DPI, but even if you fix that number, the direction to create files at 100% of print dimensions is a weird and clunky way of saying to work at actual size.