The reason the app uses its naming format is to handle R+J files – because there are two files, using .XMP for both will not work.
The app could add “I know what I’m doing” setting, but if you have R+J files, the app will destroy information (by overwriting XMP files). While it’s technically possible to have warnings for such a case, the code for saving XMP is very low level and does not the ability to display an alert, wait for you to answer, and then save, so warnings in that case are not something I’m inclined to add (this is exacerbated in cases of batch processing). So, you would _really_ have to know what you are doing….