Yes, that is a good explanation of how Verizon "shapes" (or possibly throttles) its customers' upload speeds, but as you said in your original post, it doesn't explain why Verizon chooses to do this to their customers who are paying for faster upload speeds than they are able to even come close to achieving.
Also, it would be great if other users here could test their speeds using the official Verizon FIOS speed test site to their closest server, and then compare when using the same site to a distant server, and then report their results here.
http://my.verizon.com/services/speedtest/
My download speed always stays the same no matter which server is selected, but the upload speed always tests at only about 10% of the speed on distant Verizon servers compared to what it shows at the closest server. I would expect some speed drop (on both upload and download), but not a 90% drop and on only the upload speed.
Finally, is there any way to make a single stream into a multiple stream as a workaround to get better upload speeds?