Shopify's changelog says online stores now ask customers to confirm before sending them to a website outside the store. A short message shows the site's address with the choice to continue or go back. Connected domains and supported Shopify and social websites don't trigger it, but sites you own and haven't connected might.
Shopify says merchants will soon be able to add trusted domains, such as a booking tool or partner site, under Online Store, Preferences, so customers skip the message. There is no date yet.
My read: this is a safety feature aimed at unexpected redirects, and the cost lands on your own journeys that hop to another domain, like a quiz tool, a booking page or a sister brand site. Each one now carries an extra click.