You're absolutely right. My bad.
I must still be a little bitter that Cirque du Soleil didn't hire me as a strength coach when I applied. Oh well, their loss.
As for "working out" on the agility ladder, I'd say not. Do the specific agility drills when you are relatively fresh, to best train the nervous system. Putting them in the warm-up allows one to be fresh and train their agility in a relatively "cold" state--which is likely when your agility will be called upon in real life. IMHO.
One can absolutely do a workout on a slide board. Punishing on the legs.
As for the Indo Board, I like it as active rest. I do Coach Davies' 10-minute workout on it (evenly split among balance/rocking/squat position/surf stance rocking). It might also be good as active rest in a WOD with set rest periods (obviously not "As Rx'd").