And IF two applications are deemed to be on the same invention, it prevents any argument over who gets the patent.
At the moment, the "first to invent" rule allows the second-filer to rack up large legal expenses fighting over "who really was the inventor". In "first to file", the *only* thing the second-filer can end up winning is simply to invalidate any and all patents. They can't get the patent themselves.
That's something a lot of Americans who don't like "first to file" argue wrongly. All "first to file" means is that there's no argument over who is entitled to the patent IF the patent is valid. The date on the patent application (or prior publication) is EVERYTHING. Take the patent this article is about, for example ... :-) In a "first to file" environment, all Google would have to do is produce an example of the code being sued over, prove that it was "in the wild" the day before the application date on the patent, and game over. Bedrock either fold on the spot (claiming they got it wrong and their patent DOESN'T cover the affected code), or watch their patent get killed.