Entity Framework Core 2.1 group by not working properly

I'm using Entity framework Core 2.1.4 and I wrote an basic example query from C# like below.

var myList = context.HastaAdres.OrderBy(p => p.ID).Take(20).GroupBy(p => p.IlKodu).Select(d => d.FirstOrDefault()).Select(p => p.ID).ToList();

But in SQL profiler, running code like below. There is no group by in SQL and very different from classic entity framework. So, also result is different. I need only one column as a result. But first query, return all columns. Also row count is different from second query.

SQL Generated By Entity framework Core

SELECT [t].[ID], [t].[IlKodu], [t].[AcikAdres], [t].[BucakAdi], [t].[BucakKodu], [t].[BulvarKodu], [t].[CaddeKodu], [t].[CreatedBy], [t].[CreatedDate]
FROM (
    SELECT TOP(20) [p].[ID], [p].[IlKodu], [p].[AcikAdres], [p].[BucakAdi], [p].[BucakKodu], [p].[BulvarKodu], [p].[CaddeKodu], [p].[CreatedBy], [p].[CreatedDate]
    FROM [Ortak].[HastaAdres] AS [p]
    ORDER BY [p].[ID]
) AS [t]
ORDER BY [t].[IlKodu]

When I tried this method in Entity Framework, it's generating perfect code.

SQL Generated By Entity framework

SELECT 
    (SELECT TOP (1) 
        [Limit2].[ID] AS [ID]
        FROM ( SELECT TOP (20) [Extent2].[ID] AS [ID], [Extent2].[IlKodu] AS [IlKodu]
            FROM [Ortak].[HastaAdres] AS [Extent2]
            ORDER BY [Extent2].[ID] ASC
        )  AS [Limit2]
        WHERE ([Distinct1].[IlKodu] = [Limit2].[IlKodu]) OR (([Distinct1].[IlKodu] IS NULL) AND ([Limit2].[IlKodu] IS NULL))) AS [C1]
    FROM ( SELECT DISTINCT [distinct].[IlKodu] AS [IlKodu]
        FROM ( SELECT TOP (20) 
            [Extent1].[IlKodu] AS [IlKodu]
            FROM [Ortak].[HastaAdres] AS [Extent1]
            ORDER BY [Extent1].[ID] ASC
        )  AS [distinct]
    )  AS [Distinct1]

What can be the reason of this situation?