I looked up the specifications in the service manuals. The difference in ratio is due to a change in the number of gear teeth on the first driven gear from 31 to 32. The numbers of teeth on all other gears are the same so I suspect the change was made for ease of manufacturing rather than specifically to change the ratio. The difference in acceleration between the 2011/2012 models and 2013-2017 models is primarily the programming that limits torque if you floor the accelerator on 2013 or later units.
My 2011 would give all it had to offer if I just floored the accelerator. I thought my 2015 was significantly slower until I met someone from the test track who told me to feather the accelerator instead of flooring it. The 2015 was almost as quick as the 2011 if I feathered the accelerator just right, but it was hard to be consistent--the 2011 would have been much better for bracket drag racing because it was consistent. The 2019 also benefits from feathering, but the OEM tires also limit maximum acceleration (very easy to light the traction control indicator) since they are dealing with twice the horsepower. Still, I would gladly purchase a "performance chip" to get instant accelerator pedal response if one were available in the USA and it would not impact warranty coverage.
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015; traded 8/10/2019 at 82,436 miles
White LEAF 2019 SL Plus purchased 8/10/2019