Cannot add a non-static custom thunk to a code class

In 4.19, it is no longer possible to create a non-static custom thunk in a class. This was possible in 4.18.3.

REGRESSION:
Yes.

1. Create a new Basic Code project.
2. Add a new UActorComponent code class to the project.
3. In the header file for the new UActorComponent class, add the following code:

   UPROPERTY(EditAnywhere, BlueprintReadWrite)
   TArray<FString> LineBuffer;
   
   UFUNCTION(BlueprintCallable, CustomThunk, Category = TestCat, meta = (CustomStructureParam = "AnyStruct"))
   void InitializeStruct(UProperty* AnyStruct);
   
   DECLARE_FUNCTION(execInitializeStruct)
   {
   	LineBuffer.Add(TEXT("This is a test."));
   }

4. Build the project in Visual Studio.

RESULT:
The build fails with the following error: error C2228: left of '.Add' must have class/struct/union

EXPECTED:
The build completes successfully.

Can anyone help me recreate this materials in UE5?