Query: Incorrectly ignored include with GroupBy

[smitpatel]

    public class Blog
    {
        public int Id { get; set; }
        public string Author { get; set; }
        public List<Post> Posts { get; set; }
    }

    public class Post
    {
        public int Id { get; set; }
    }

Query

    var query = db.Blogs.Include(b => b.Posts)
        .GroupBy(b => new { b.Id, b.Author })
        .GroupBy(b => b.Key.Author)
        .ToList();

Generates

warn: Microsoft.EntityFrameworkCore.Query[10106]
      The Include operation for navigation '[b].Posts' is unnecessary and was ignored because the navigation is not reachable in the final query results. See https://go.microsoft.com/fwlink/?linkid=850303 for more information.

But the result does contain Blog and posts should be populated.
EFCore 2.0.2/2.1.0-rc1

[smitpatel]

Blocked on #17068

[smitpatel]

As per #17068 not supported query.