I just realized that the .xml file fix was not part of the change either. Please see my full request here:

https://github.com/joomla/joomla-cms/pull/230/files

@spignataro in your tracker item, you stated

Go to that article in the Content Manager and choose the layout override

It looks like you may be right - I will perform a test next week when I get a chance to fully review. But it looks like you are correct by reviewing the ocde.

Any update on this PR?

You are correct - we don't need to add a field. Sorry I forgot to post back to this. Thanks for the follow up.

Are you sure this is a bug? Because when you set a menu item to show a single article, the article options are not relevant. Those from the menu item will override it.
Thus if you want an alternate layout, you need to set it in the menu item instead, not in the article. Menu item takes precedence over article item in this case.
It's another case if the menu item points to a different view, for example the category view. Then the article parameter will be in effect and the layout set in the article should be chosen instead.