This was discussed in #112022 and on devtalk:
https://devtalk.blender.org/t/vertex-groups-generic-attributes-and-name-clashing/31073
While vertex groups with the same name as attributes should be avoided, since
it can cause ambiguities when using attributes, it's something we can handle
gracefully for now. Enforcing unique names for vertex groups resulted in breaking
other functionality under some circumstances.
This effectively reverts 12ef20990b, except for
the bug fix in `BKE_id_attribute_new`.
#112891 adds a warning to avoid make users aware of duplicate names so that they
can be avoided in practice.
Pull Request: https://projects.blender.org/blender/blender/pulls/112889