The relevant excerpt from the service document:
Keyboard and Keycaps
The keyboard has a membrane under the keycaps to prevent debris from entering the butterfly mechanism. The procedure for the space bar replacement has also changed from the previous model. Repair documentation and service videos will be available when keycap parts begin shipping.
More details to follow…
In an internal document distributed to Apple Authorized Service Providers, obtained by MacRumors from a reliable source, Apple has confirmed that the third-generation keyboard on 2018 MacBook Pro models is equipped with a “membrane” to “prevent debris from entering the butterfly mechanism.”The relevant excerpt from the service document:In its teardown of the new 13-inch MacBook Pro with Touch Bar, the repair experts at iFixit were first to discover the thin, silicone barrier underneath the keycaps , and theorized that it was to prevent dust indeed.More details to follow…
More Info: www.macrumors.com