...snip...
When batch 1 shipped I expected a sharp immediate diff increase which did not happen, same with batch 2. I suspect they simply unplug a miner and ship it off and then over time replace them with new ones as they get off the assembly line. This explains why the diff increase has been gradual when new batches ship rather than an immediate sharp spike.
This is my assumption based on observations also. The peak is slowly going up as devices come online "permanently" with end customers.
-j