If you were about to go through a channel to find your mention then it will take all day long.
You could allow this just in case someone mentions something worth looking into, but you can also completely disable this as well.
People who were offline that were going to come online were probably not going to be experiencing the downtime by the time they were online unless it was a major outage.
Also, is there any difference between the two commands? Select the role you wish to assign the user by checking the box next to the role name.