Thank you for your feedback.
Please keep in mind the use case @ohrenkino mentioned:
For files loaded the very first time it could be that even if you don't change yourself anything in your tags they could by changed if you press the OK-Button.
The settings in Mp3tag -> Tags -> Mpeg could cause an "internal" change in your files adding - for example - ID3v1 tags. Or another UTF-/ISO format according to your Mp3tag settings. Or removing APE tags, again according to your actual settings.