https://arstechnica.com/gadgets/2018/07/new-macbook-pro-keyboard-design-may-fix-dust-problems-after-all/

While Apple's redesigned keyboards in the new MacBook Pro models are made to be quieter, they also appear to be designed to prevent another problem. According to a document sent to Apple Authorized Service Providers and obtained by MacRumors, the new keys have a "membrane" underneath that helps "prevent debris" from getting into the butterfly mechanism.