SourceGenerator is not working with .net48 as nuget package reference

I have netstandard2.0 soruce generator project which I consume from .net6 and netstandard projects as nuget reference, it works fine with .net6 and netstandard but when I add nuget reference to net48 projetc, its not working, If I add project reference rather than nuget reference, it works in that case, thats weird behaviour I couldnt understand