This kinda almost makes it sound like VisiOn introduced Gates to the GUI which is not true. They were already using and developing for Macintosh machines at Microsoft and had hired Charles Simonyi from PARC with his expertise in GUI systems before Comdex 1982.

The story seems to be more that seeing VisiOn gave MS the nudge to get into action on the GUI due to a sense of competition/urgenbcy from VisiOn rather than learning about the GUI from VisiOn.