Well, here's my theory. Somewhere along the way Triumph revised the lifter piece. The original design had a narrow shoulder that used a washer (the one in the illustration, not the wavy washer) to increase the thickness of the shoulder. The revised lifter piece had a thicker shoulder that eliminated the need for the washer. You have the revised lifter piece with the thicker shoulder that only needs the wavy washer.
There are pictures comparing the two lifter pieces side by side somewhere on the forum, I'll try to find them or someone else will if I can't locate them.