Net48 is not compatible with WCF6.0 packages when projects specify multiple target frameworks

[JiakaiDou]

Describe the bug
Specifying multiple target frameworks Net48 and Net6.0 in the project, adding a WCF service reference, and then building the solution, I get an error that Net48 is not compatible with the WCF6.0 package.

To Reproduce
Steps to reproduce the behavior:

1. Create Net6.0 TargetFramework project, e.g., Console App
2. Open .csproj file, change net6.0 to net6.0;net48, delete ImplicitUsings and Nullable those two properties
3. Go to Program.cs file, add the following sample code. Save all changes.
4. Add WCF Service reference
5. Build solution

Expected behavior
The code is generated without error and the project builds successfully.