A group with this name already exists

Hi, i've just created a profil named my_name

then i try to create a group named my_name on the same instance

i have the error message : A group with this name already exists

I smell the name space is the same so i delete my profil named my_name

then i try again to creat a group name my_name.

i still have the error message : A group with this name already exists

So my_name is reserved for ever but unusable ?

Is it a feature (with a lack of contextual documentation) or a bug ?