MSBuildSdkExtras: VS 2017 15.6+ breaks UAP builds

I just wrote a post with the following example repository:

https://github.com/GeertvanHorrik/MultiTargetingProject/blob/master/src/Ghk.MultiTargeting/Ghk.MultiTargeting.csproj

Then I read about the new 15.6 method to include the references, so I made the following changes.

Changes

1. Replace <Project Sdk="Microsoft.NET.Sdk"> with <Project Sdk="MSBuild.Sdk.Extras/1.2.2">
2. Remove <Import Project="$(MSBuildSDKExtrasTargets)" Condition="Exists('$(MSBuildSDKExtrasTargets)')" />
3. Remove the package reference to MSBuild.Sdk.Extras

Result

========================================
Build
========================================
Microsoft (R) Build Engine version 15.6.82.30579 for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.

C:\Source\MultiTargetingProject\src\Ghk.MultiTargeting\Platforms\uap10.0\Views\MyView.xaml(1,23): error MC3074: The tag 'UserControl' does not exist in XML
namespace 'using:Catel.Windows.Controls'. Line 1 Position 23. [C:\Source\MultiTargetingProject\src\Ghk.MultiTargeting\Ghk.MultiTargeting.csproj]
C:\Source\MultiTargetingProject\src\Ghk.MultiTargeting\Platforms\uap10.0\Views\MyView.xaml(1,23): error MC3074: The tag 'UserControl' does not exist in XML
namespace 'using:Catel.Windows.Controls'. Line 1 Position 23. [C:\Source\MultiTargetingProject\src\Ghk.MultiTargeting\Ghk.MultiTargeting.csproj]
An error occurred when executing task 'Build'.
Error: One or more errors occurred.
        MSBuild: Process returned an error (exit code 1).