The changes added have to do with the rotorwash across the disc as helicopters move. On the video (which you can find above), Austin Meyer, the CEO of Laminar Research explains the concept as well as a bit of the calculations included.
This is a companion discussion topic for the original entry at https://www.helisimmer.com/news/laminar-research-closed-x-plane-11-40-beta-include-helicopter-tilt-rotor-changes/