If your institution uses Blackboard Ally, then the DesignPLUS default of hiding the Canvas title is disabled. The tools will show the Canvas title because the Ally alternative formats dropdown button is appended to that h1 title and that button needs to display.
Alternative Formats
Legacy Design Tools Sidebar
MARCH 2021 UPDATE: Admin option to move Ally dropdown out of the title. We now have an option for a Canvas admin to move the Ally button out of the Canvas title so that it can still display and DesignPLUS can hide the h1.
New DesignPLUS Sidebar
The option for a Canvas admin to move the Ally button out of the Canvas title can be adjusted in the Account Settings tool. For more information on moving the Ally button, see our Admin Guide: Instructions for Customizing Account Settings under the Ally Dropdown Relocation panel.