Today the Sim Update 6 flight users were purged on the back-end of the Sim Update 6 flight. PC users will see an update to the sim to the same build number 126.96.36.199.
If your content is installed in the default location C:\Users[user]\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache\Packages, you will experience a full re-install. If your content is pointed to another folder you should only need to update the 1.6 GB exe file in OneStore and point to your content.
This behavior will be true for all future Insider Hub OneStore Flights and will be included in future flighting prep communications. We highly encourage installing to another location to avoid this behavior.
In the future, we will time these updates with major releases to avoid this kind of update delay. Thank you for your time and willingness to provide feedback for MSFS.