It depends on the purpose of the app naturally, but I’d suggest that for certain mobile apps which are cut-down versions of full desktop apps, and where many users have a preference for the mobile app, that the mobile appeal is due to simplicity, and that the simplicity is part due to size restrictions forcing designers to make the apps more task focussed. So lack of space has helped to increase usability.
Whichever way you look at it, I’d like to have the option of running simpler and more task focussed mobile apps on the desktop regardless of the size they assume. Given that I’m happy to use them on a mobile sized screen, running them at that size on a desktop wouldn’t be a problem, and given that some mobile apps are quite utility-like, I’d probably run lots of them simultaneously. That’s what led me to discuss window layout awkwardness.