I think you're missing the point of touch mode: mouse and touch actually work fine in both modes. The touch mode is just there to demonstrate how Flutter adapts the layout depending on the target modality: see how the controls get larger when you select touch mode.

The Medium post[1] about Web support explains some adaptations they made for Desktop browser, including:

  We also increased the default content density, because mouse pointers support a tighter density than touch devices.

I expect that in a "real" app the default mode is adapted automatically based on the device type.

[1] https://medium.com/flutter/flutter-web-support-hits-the-stab...