All, there is a new “feature” in the latest mobile app version 2.3.
It is not stated up front, but this new lan discovery automatically adds all discovered devices without the ability to exclude them.
Even after you manually remove something it discovers, simply going back into add a device will add it back in.
Why is this an issue?
Well, smartthings logs everything immediately and you may not be aware a device it quietly added in the background is now logging all its usage to the cloud without your knowledge.
This should be made much more clear to end users and should allow you to add the devices or exclude them, instead they opted to add them all automatically.
Just my two cents.