Fortnite has had a single release and is a free to play game. Once again, if you're going to point out games that just come out with a new version to sell it again, you're failing to show accurate examples.
Bethesda is also notorious for taking forever to make Elder Scrolls games. Skyrim came out in 2011 and has not had a proper sequel since. First-person RPG also isn't exactly a glutted sub-genre. Neither of the examples fit the phenomenon they're talking about!
I wouldn't say notorious. It's only become that way with the latest games. Morrowind to Oblivion was ~5 years. Oblivion to Skyrim was ~5 years. Fallout New Vegas (Obsidian) to FO4 (BGS) was 5 years.
It's really only since then that game development times have skyrocketed as much as they have.
That's fair. The ancestral post's claim of "every six months" is still ludicrous, just not as cartoonishly so. It's not like Bethesda RPGs are licensed pro sports games or Assassin's Creed.