To sum up Dave's report, he had heard from his dealer's service department that one of their Techs had discovered a SW patch for the LEAF's BMS, but the tech was on vacation until August 1st, and know one else in the shop knew about this update. Dave in the mean time made an appointment to have this update installed.
To me this simply did not pass a basic sniff test, and my research could not find any TSB for the LEAF that would fit the description of this kind SW update, but did sound very much like the update last year for the 30kWh cars and the phantom degradation bug.
So I went a bit further and reached out to Nissan this morning to get more information on this, and here is the response I received from Jeff Wandell from Nissan's Product and Technology Communications:
"I can confirm that a software update that reduced the quick charging safeguards was offered to customers in Europe. We’re currently investigating offering the software in the U.S. for 2018 – 2019 40 kWh LEAFs but have nothing to announce at this time.
As things progress forward, I’ll let you know of any changes".
So in summary, no there isn't a charge speed update at this point in time. There may be one in the future, but not today.