I know Supercharging/CHadeMO is a different type (DC) charging than the NEMA 14-50 (AC), but does the charging profile look the same? In other words, does the charging slow down as you get closer to a full-battery?
Yes, and the higher the power, the sooner it slows down. The Supercharging web page says the first 80% takes the same amount of time as the last 20%.
It seems to throttle back to about the same charging power (taking into account that the DC power is about 90% of AC power) vs State of Charge. This is why the last few percent take just as long on a 14-50, an HPWC, or a Supercharger, i.e. FOREVER, if you are waiting.