My Maverick 88 was made in the early ‘90s, and it has dual action arms. The Mossberg 500s had single arms once upon a time, too. I once owned a 1965-vintage gun with a single (highly flexible and sticky) arm.
Both the Maverick and 500 had single arms at one time. Heck, every Maverick I’ve seen had a single arm. Was enlightened on this thread that they had a second added.