They use the word mock several times to explain stubbing. I think they mean stubbing is a type of mocking not an independent approach. They even use a mocking library to create stubs in the Google article.
"Mock" can be both a noun and a verb. As a noun, it's an alternative to stubs, fakes, and other such things. As a verb, it refers to the "monkey patching" method of putting those into place, in a way that undoing it is automatic and won't leak into other tests. The title seems to be referring to this second version, showing us ways to avoid patching with things like dependency injection.
Indeed, like people stating something is a deferred or a future instead of promise, and then pointing out a minor difference in their approach that justifies a whole new taxonomy.
