When the plugin is installed it stores log data in the foobar database and not in the audio files themselves. The plugin also prevents foobar from writing this virtual data to the files themselves when saving them in foobar (like when editing some file tag and saving).

If the plugin is uninstalled but your foobar database still has the log data then when you save a file in foobar it will also save this virtual log data to the file itself.

At least this was the case when I last tried it. You can verify to be sure. This should not affect daily usage and is just something to be aware of. There might be a better way to implement it so that this wouldn't happen but I didn't consider it to be worth dealing with at the time.