The Develop module no longer properly renders the Grain Effect settings in LrC 10.2, which appear much more pronounced and correct in the Library module and exported files. I tested with GPU enabled and disabled with LrC restarted and the issue persists on my Windows 10 system.
The below screenshots are with LrC 10.2 using Grain settings Amount 100, Size 50, and Roughness 100.
Updates to the Adobe Photography Products were released today and contain a fix for this issue. Please install the update via your Creative Cloud Desktop App or your respective App Store. Note: You may need to refresh the Creative Cloud App for desktop software to show an update available. ([Ctrl/Cmd]+[Alt/Opt]+ [ R ]) For Mobile downloads, it may take several days for the update to appear in your respective App Stores. Thank you for your patience.