In version 7.0 we introduced ability to use LLD group prototypes even if a group with the same name was already created by another LLD:

Sharing discovered host groups

Low-level discovery rules can now link already discovered and existing host groups to hosts created by the same low-level discovery rules. This affects host groups previously discovered and created by other low-level discovery rules based on the specified group prototypes.

But there is still a problem if a group with the same name was created manually (or by API):

In many scenarios such a group could have been created already and might have been created automatically by API.