Can you share the specific passages where we say this?
Any website / web-app built using Builder does not become AGPL if it only uses API calls, the same way any application that runs on Linux does not automatically become GPL (all apps running on Linux use Linux API)
The goal behind making these apps AGPL is that anyone who runs modified versions of Builder or CRM should give the same rights to the users, anyone who uses them as API backends does not have to make their applications AGPL.
Hope that is clear.