Isn't not letting C students graduate a good thing?
If you paid course fees and did the work, you should be able to walk out and say 'I am a C student at RoR' with a certificate.
A company which hires through boot camps can ask for grades and choose to hire or not.
A C level student with other skills may still be valuable because of other skills they have and employable for junior or non dev roles.
Setting such a high bar pretty much just seems to be a way to manipulate data for marketing purposes.
My reaction was, "Well we would likely reduce the rate at which security vulnerabilities are introduced in new code."
Then I reread it. :-)
(And I criticize C with love. I used it for years and recognize it as a product of its original purpose.)