Specifically, the US version of the MacBook Pro Service Readiness Guide apparently links to a separate document called "Butterfly Mechanism Keycap Replacement MacBook Pro (2018)." MacRumors reports that it contains the following language: "Caution: The keyboard has a membrane under the keycaps to prevent debris from entering the butterfly mechanism. Be careful not to tear the membrane. A torn membrane will result in a top case replacement."
This isn't really a surprise. Apple is already facing a class-action lawsuit over these keyboards, which are expensive and difficult to repair and prone to breakage. The company has also instituted a service program to repair or replace keyboards free of charge for certain models. While the company doesn't want to add credence to the lawsuits against it, it clearly is taking steps to address the reliability of its keyboards.