Wait... I'm confused about Guam being included in the list of new countries where Project Fi can be used.

Just checked my records and I had my Project Fi SIM(in old Samsung Galaxy S7 edge) with me in Guam during the last two weeks of August 2017. It worked fine... Not sure how it worked because i never thought about it. (most likely I just assumed that since Guam is the United States, it should have just worked) Was that just a fluke?