Sam Lionheart of iFixIt recounts a deeper test of the new MacBook Pro keyboard, including dumping dust and sand on the keyboard until it fails:
We started with a fine, powdered paint additive to add a bit of color and enable finer tracking (thanks for the tip, Dan!). Lo and behold, the dust is safely sequestered at the edges of the membrane, leaving the mechanism fairly sheltered. The holes in the membrane allow the keycap clips to pass through, but are covered by the cap itself, blocking dust ingress. The previous-gen butterfly keys are far less protected, and are almost immediately flooded with our glowing granules. On the 2018 keyboard, with the addition of more particulate and some aggressive typing, the dust eventually penetrates under the sheltered clips, and gets on top of the switch—so the ingress-proofing isn’t foolproof just yet. Time will tell how long the barrier will hold up.
Also of note: It looks like the keys on the keyboard have been redesigned to make them more readily removed and replaced, including the space bar (which previously couldn’t be easily removed without breaking the mechanism). So in addition to better guarding against fine-particle ingress, this keyboard seems to be designed to be more repairable.