Further to this thread where we found solidworks allowed you to delete parts from sub assemblies that you weren't expecting to edit:

https://forum.solidworks.com/inbox?objectType=2&objectID=337558

I just discovered another trap for the unwary.

Create a sub assembly where one of its parts has several configurations.

Then make the sub assembly have configurations each with a different config of the part active.

Now put that sub assembly in a top level assembly.

Obviously you can select that sub assembly and change its properties to reflect its different configs.

right click configure component is not available unless you select the sub assembly rather than the part - quite rightly.

However now click on the sub assembly component that has configs. in the resulting pop up box you can change that components config - try it. Unexpectedly that just edited the sub assembly which is not open in context and not open for editing! You better remember what you did because no undo is available! (though if you spot it before saving you can re-load the sub assembly...)

I might have a left and right configs of a part, and then typically I would name the configs of the sub assembly left and right too, and doing that makes it very easy to edit the sub assembly accidentally.

This is very similar "enhanced" but dangerously confusing functionality to deleting sub assembly parts discussed in the link above. Probably it came in under the radar in 2013 like the delete issue - I wonder if there is also a solution in 2015?