Redpoint5 wasn't asking for the engineer's credentials. He was asking for a citation/source of the specific claim.
Unfortunately, a lot of the press materials for the Bolt's introduction have been scrubbed from Chevrolet's website, but
multiple websites' articles from the time report that GM said one-pedal driving would add "about 5% range" in stop-and-go traffic. Using the Bolt's EPA range of 238 miles at introduction, that's 12 miles--not 40.