Why can I see a sales user under the Modified By column in the Opportunity Settings Page?

Only admins can access the Opportunity Types Configuration page. However there are instances when sales users appear under the Modified By column on the Opportunity settings page –

This occurs when the allow auto update setting is enabled for a drop-down field within an Opportunity Type.
With the Allow Auto Update setting enabled, when a sales user enters a new value/option while filling the drop down field (through a form, opportunity import or API call), the opportunity type is modified and the user’s name appears under the Modified By column on the Opportunity Settings page.