In short, Grinding Gear Games is changing the way they store data and internal files. To that end, a full redownload of the game will be required. GGG acknowledges the hassle this creates, but state they, “felt it was better to only do the full re-download once and to simultaneously include enough additional benefits that we feel it's definitely worth it for everyone.” Note that you won’t have to uninstall and reinstall. Patch 3.11.2 will automatically perform the redownload.
Additional performance and technical changes brought about with this new patch includes faster patching, improvements to Steam patching, preloading improvements, improvements to texture quality, re-exported audio, improvements to the engine, and more.
Additionally, a macOS client for 3.11 Harvest League will be made available for testing. After the deployment of patch 3.11.2, GGG may post a link to this client for download and feedback. Finally, after 3.11.2, an Epic Games Store version will be listed. You can read the full patch notes here.