Interesting. I did a bit of digging and the disclaimer about not being an officially supported Google product was there from the start. There was briefly a logo that used Google colors[0] but it seems extreme to fire someone over such a small misstep. I'd say either HR gave him a bogus reason like you said or he's not telling the whole story.
Also more interesting is the fact the repository is still alive and kicking.
I can see Google firing the dev but HR/Legal giving a bogus reason, as is regular practice.