Fillet function changes volume tag

I construct a volume (here a cylinder) with some volume tag (here 42) and apply the Fillet function. That changes the volume tag (here from 42 to 1). I think it is set to smallest free volume tag. Is this behavior on purpose? If yes, why? In my opinion this can become problematic if one wants to work on this volume later (for example assigning it to a physical volume).

Thank you in advance:-) Fabian fillet_function_changes_volume_tag.geo