This is not typical behavior, and I’ve never heard of it before. When you add a file to a Batch, nothing should happen except that file was added to the batch, nothing should be automatically applied. Did you create any custom presets or custom destinations. I’d sure love to see a screen recording of this in action.
So, there’s some typical troubleshooting we can try. First is to go to the Preferences for Compressor, in the General tab, verify default settings for jobs and destinations.
Next, go to the Advanced tab, click the Reset Queue button, select Cancel Jobs, click the Reset button Go back into Reset Queue again, this time select Repair Compressor, click the Reset button. Quit and relaunch Compressor. See if this helps.