IMPORTANT: Although Kiddo Diapers is the merchant here, Kiddo Diapers is not the problem. They have no part in this besides using Shopify as their e-commerce platform. The real problem is Shopify.
I ordered some Kiddo Ultra Drys on launch day. I always, ALWAYS use separate browser profiles for any ABDL activity. Private user profile on my Android phone, separate email, separate phone number, not logged in to my Shop.app account. I can't log into it from that browser. It literally doesn't have access to the passkey.
The other night, I logged into my vanilla shop.app account and there was a giant banner on the homepage for Kiddo Diapers.
I looked through my profile. There was no order history for them and they were not under my followed merchants.
This means they matched only based on either my name and address, or my card info. And card info is usually tokenized immediately so it's next to impossible to build secure systems that correlate it between UIDs. So it's probably name and address that matched in their recommendation algo.
The only way I can find to avoid creating this association is to not use a shop.app account at all. Which is a darn shame because the checkout experience was pretty convenient otherwise.
I've tried to get in touch with their privacy team but in the meantime, if you have a shop.app account and you order ABDL stuff to the same address and name as vanilla stuff, beware it will get associated with your account whether you want it to or not. The only way to protect yourself is to delete your account.