I discovered this a while ago and thought it was a little, mostly harmless bug, but I’ve since realised that once you’re aware of it, it can be a useful feature. Whether or not it’s intended behaviour, I’m not sure!
If you make a multi-selection, and do an operation on it, the results may differ depending on how you made the selection. For example in the set list, if you select a bunch of adjacent songs, starting with your selection near the top and extend the selection downwards, then right-click and choose “Re-assign Program Numbers”, the numbers are assigned in the expected order. But if you select the same songs, but this time start with the bottom one and extend the selection upwards, the re-numbering happens starting at the bottom song.
Another example - if you make a multi-selection of routes, and then paste, they’ll either be pasted in the same order, or in reverse order, depending on which direction you made the multi-selection.
This is not standard selection behaviour for most software, which generally ignores how a selection was created and maintains the order regardless. But it’s potentially useful, if you need to reverse the order of some things 
Neil