This will be helpful to choose a default out of two or more sources used in a created page. Currently users see the first listed source when they open a page for the first time. And can be confused of the wrong data they see on the screen.
The order in the settings of a page below does not affect on how the models will be ordered as sources of this page.

The order anyway will be alphabetical now. So the only way to affect on the order - meaning on the default option now - is the renaming of both WS and models used as sources. Which is obviously not the best solution.

"Sources ordering" or "Default source" feature is essential for this cases where access for various models required in one app.