I don’t think that’s correct. There are lots of things in userdata that needs to be fixed to work in OH 3. If you just copy them over there is no chance to fix them. I believe the advice is to install 2.5, copy your 2.5 config, then upgrade that to 3. But that’s on Linux. I don’t know about Windows.
Not surprising since one of the thing that needs to be fixed is the names of the Things. It’s a simple find and replace. Any reference to org.eclipse.smarthome needs to be replaced with org.openhab.
Same problem.
We’d need to see error messages to find out what’s going on with that.