One of you are insane, but obviously, it's not you :)
From the layout drawn, they are setting the joists on top of the beam, now comes the problem - with a deck panel installed as shown on the sketch below (note that the deck panel can be in any orientation), if you step on point "A" of the cantilever joist, point "B" tends to tip up, as it is not supported by anything but jointed by the deck panel and the edge board (if there is one). Similarly, when you step on "B", "A" will lift up. THe joist is unstable, thus it needs to be corrected.
IMO, the easiest way to fix this situation is to shorten the overhang of the joists as shown below.