When you check the box for auto provisioning users as part of the sso process, there should be a selection called “Default access level when auto provisioning” with a drop down where you can pick from a list of the access levels you’ve created.
It is set to "Requestor" by default, but from what I read in Workfront community people want the default access level to be set to "Reviewer" and this is something our Org wants as well.