And I immediately think “the mushroom strain?”

I would guess the main purpose of the hatch is to prevent the dogs freely leaping between yards unsupervised.

CAPTCHA was never about keeping bots or AI out. It was always about tracking people. That’s why you get more of the “select correct images” CAPTCHAs the more you hide who you are online. It’s not that they are trying to figure out if you are a bot, it that they are trying to figure out who you are period. Interactions with a site exchange information the more interactions the more information they get. Also they can’t make a profit selling your information, they might as well use your free labor to train their AI.