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.

Also https://www.martinfowler.com/articles/mocksArentStubs.html

Mocks are for objects, stubs are for responses and ‘fakes’ are basically the same thing as mocks.

Fakes are not mocks. A fake is an actual (simplified) implementation of the dependency.

For example, if your dependency is a distributed key-value store, a fake would expose the same API but using an in-memory hashmap under the hood.

Yeah no, that’s a mock. At least, that’s been a mock ever since I started prgramming 15 years ago. Only later did libraries that automatically mock dependencies appear (and I presume people suddenly felt a need for a new name for not-automatically mocked dependencies?