I have a pretty consistent issue where I have an assignment using an External Tool (Skillable lab - could be any Skillable lab) and if a student cancels that assignment without completing any portion of it they always receive a score of 10/10 or 100% (depending on the grading method). I would have expected the student to receive a grade of 0% or incomplete. I have not heard of any issues like this from users other LMSs who use the same External Tool. Could the assignment have been configured incorrectly in the course?
This seems somewhat related to this post from @Carter41 :
https://community.canvaslms.com/t5/Canvas-Question-Forum/External-Tool-Assignments-Are-Auto-Grading/td-p/542313