Interesting. I've never seen a problem with Sea-Doo, Polaris, Tigershark, Yamaha, or most Kawasaki spark plugs, they all come out easily without anti-seize. I work on a lot of salt water skis. On one Ultra 250, the customer broke off 2 plugs and I had to pull the head. On another one, the plugs were really tight but did come out. The problem with Kawasaki 4-stroke owners is, they over tighten the plugs, not lack of anti-seize. The plugs have a very small thread diameter (9mm) and the torque (with dry plugs) is 115 inch pounds for Kawasaki 4-strokes.
I did look in my Yamaha manuals and I see in some of the 2-stroke manuals, it does recommend anti-seize but not in the 4-stroke manuals.
This is my experience with them. Have you had problems with dry plugs?
Chester