Also seconding the confusion that other commenters have regarding the "three commits max" rule for automated deploys. Maybe engineers at Facebook are just big fans of rebasing, but I often make commits on feature branches that don't "stand on their own" - i.e., would break some functionality without subsequent commits. I'm not sure why you'd want to deploy one-commit-at-a-time unless you kept a very strict "one commit == one standalone feature/bugfix" rule, which isn't mentioned in this post.

(I suppose it's also possible that that's referring specifically to merge commits into master, which would make a lot more sense to me)