This is an odd one and I'm wondering if we can just confirm here that it is some weirdness created in EE 2.8.x.
I just had a NavEE user contact me that when INSTALLING the module, they are seeing the message, "All data associated with this fieldtype, including all associated channel data, will be permanently deleted!".
It seems to me that this message is here in error - but I wanted to confirm. I can replicate the issue when installing addons in EE 2.8.