No Way!
That arm is nowhere near 20 lbs.. It is up there, but I would guess from past experience,more like 8-12 lbs. I would be more concerned with the weight of the whole unit which will include the washarm. I am sure someone here will have a sales brochure for them. If not the 11-12, then at least the 14's which would have been a bit heavier. That will give you a good estimate for the shipper.
The damned tank and frame on them were so beefy.Not to mention the pumps. That is what makes up all of the machine's heft. The washarm should be of little concern when you consider the whole machine would be well over 100 lbs!