Note that the "connections" checkpoint was functionally PreCheck when I used it the one time I've entered through the new SEA Customs hall (in February). Shoes stayed on, laptops and liquids stayed in my bag, and I walked right through with no wait, even though it wasn't signed PreCheck. But I've only flown through there once (since AS has only intermittently flown their YLW flight of late and it's scheduled to be useless for connections most times I try).