Tesla basically has three options when software limiting - they can limit the top and use the bottom 80%, they can limit the bottom and use the top 80%, or they can split it somewhere in the middle and limit both ends.
When they did the 40s as limited 60s, they limited the top, and the accepted wisdom of the forum is that they've done that again - but AFAIK that hasn't been positively confirmed.
If we can get a video of a 60 supercharging or at least some pictures of the Voltage/Amperage near the top of the SpC session, we should be able to figure it out by comparing to Voltage/Amperage for a 75 SpC session.