ISSUE RESOLVED!
When I bought this 513303 hub from Detroit Axle, it came in a 2-pack. I spoke with Martin at Detroit Axle customer service. He told me his system shows a 513303 and 513220 hub are interchangeable. He said I may have a damaged part, and he would ship me another 513303. I asked him to send me (2) 513220s since the 513303 isn't working. He agreed to send it.
While waiting for the parts to arrive, I bought this magnetic field viewing film from Amazon for $18.99.
https://www.amazon.com/dp/B0BCFM83XB?ref=ppx_yo2ov_dt_b_product_details&th=1
When the film arrived, I checked the new 513303 hub from the box and it has 96 magnets in the encoder.
When the new hubs arrived, I pulled the suspect one off the car and found it to have 64 magnets in the encoder. The hub on the left is the new 513303. The one on the right is the suspect one. You can easily see the difference.
I compared a 513220 and found the bearing housing to be a little different, but it had 96 magnets in the encoder. The hub on the left is the 513303 from the car an the one on the right is the 513220. See the straight sides on the 513220 vs the scalloped sides on the 513303.
So I installed a 513220 and took it for a ride. ABS light is off and the speedometer is within 2 mph at 60 mph, which is within normal range according to what I've seen posted out there.
I will be returning the defective hub to Detroit Axle. It's worth noting their customer service has been great. They provided me 2 513220 hubs at no charge trusting me to return the 513303s and they sent a return shipping label.
I'll be checking every hub I install now with my new magnetic field film before I install it.