by Marcus Green.
Here is the readme text from the source code at (note the end of the second paragraph)
https://github.com/marcusgreen/moodle-gradingform_btec
Advanced marking plugin for the BTEC marking scheme based on Refer,Pass, Merit and Distinction where each level is based on completing all the next lowest. So to get a Merit a student must achieve all Pass and all Merit, and to get a Distinction to get all Pass and all Merit and all Distinction. If they miss a Pass criteria they get a refer. If the assignment has only Pass criteria and the student gets them all the mark will be an overall Distinction. If the assignment has Pass and Merit criteria but no Distinction criteria, and the student achieves all available criteria the mark will also be an overall Distinction.
The logic is that if you don't set it to Distinction when all criteria are met there is nothing to make it clear that there are only Pass and Merit criteria and so a tutor might think a student has missed some criteria. In this context Distinction stands in for "All available criteria met".
I think this was an arbitrary decision by me to try to ensure that the results displayed makes sense.