Describe the bug

SplitButton doesn't behave as split button using touch.

Steps to reproduce the bug

1. Create a split button with a default command and drop down (e.g. with content 'Play')
2. Try clicking the "button" part with the mouse => works
3. Try tapping the "button" part with touch => shows dropdown

Expected behavior

Since a default command is bound to the button, I don't want to repeat myself inside the dropdown for touch (otherwise I would have used the DropDownButton). I would expect the SplitButton to be invoking the command when tapping the button part.

Screenshots

Using mouse:

Using touch:

Version Info

All windows versions (Windows 10 Mobile, and the 1809 update on a surface tablet)

NuGet package version:

<PackageReference Include="Microsoft.UI.Xaml">
  <Version>2.0.181018003.1</Version>
</PackageReference>

Windows 10 version:

• Insider Build (xxxxx)
• October 2018 Update (17763)
• April 2018 Update (17134)
• Fall Creators Update (16299)
• Creators Update (15063)
• Anniversary Update (14393)

Device form factor:

• Desktop
• Mobile
• Xbox
• Surface Hub
• IoT

Additional context