It wasn't like this at the beginning, or I didn't pay attention, but I can not add ONLY Jira Service Management product to a user (Agent, not a Customer type). Jira Software adds automatically.
I was sure that it was two different products with separate licensing. Either I didn't pay attention to it at the beginning (we started from a couple of admins with all products), or there are some product settings that affect it and "link" this access, or it is a bug.
p.s. if I remove the product access to Jira Software from a user, JSM also disappears.