Fix Broken Links annoys me.
But, yes, that's probably expected if you manually kicked off a Run Auto Import Now. Remember, otherwise it only runs on particular files when it receives a filesystem notification event. Running it manually (a full scan) tells it to, essentially, check all the files. So, it did, and the drive was probably 1/2-way mounted (so, it existed, but the files "didn't").
There's only so much logic they have to decide if the drive exists or not. Another thing that will insta-delete your whole library is if you mount another drive with the same drive letter as your Library Drive accidentally (or intentionally).
So, if you're running that manually (or scripting it) and your network drive is unreliable or not always mounted, you need to be careful or disable that (would be my recommendation).
I've ranted about that feature many times before, so you don't have to convince me it is "broken" and quasi-dangerous.