IIRC, the Unitarian Universalists do ordain atheist pastors, so an atheist would not (and should not) have to fake it there.

But more to the core of your point--yes, someone could fake their way thru the process, just as they could in other professions. There are doctors and nurses who discredit medical science, biologists who discredit life science, journalists who discredit journalism, etc. If they made it to where they are, of course there can be pastors who faked it as well. As to why that is, I think we as a society will make choices to reward fakery rather than truth for reasons of convenience. I wish that were not so, for my profession and for others.