Yes, that is true. But the hypocrisy is how Firefox criticises Google (either directly or indirectly), but is paid by Google to have them as the default search engine. The emphasis is on the word default, not that you can't change it. The same thing goes for Apple with Safari. They disabled 3rd party cookies and promote privacy, but Google is still the default browser, for which Google pays a very large amount of money each year.

They (implicitly) critisize some of Google's behavior, while taking Google's money, yes. What makes that hypocrisy? It would be hypocrisy if they were doing what they are critisizing; it's not clear to me it's hypocrisy to take money from someone who is... while still critisizing them! not critisizing them because you are getting money from them might be hypocrisy...

In the context, most users do not change the default