Bitrix: Insufficient rights to view the list of all users when editing a group. What is the reason?

Question

1C-Bitrix

Good afternoon.
For the group, set the rights:
1) Main module - User management.
2) Training module - full access to settings.
However, when users of this group edit the Learning Group (Services->Training->Groups), in the Group Membership section it says "Insufficient rights to view a list of all users."
What could be the reason?

Answer 1

And what operations does this access level "User management" contain in the Main module?