> CS degrees are not standardised
In most countries they are, by law. Is the basis of the educative system. Degrees are certified and strongly regulated by the government. I can't just print and flash one without a license to emit degrees. This would be to falsificate a public document, wich is a crime in most countries in the world, if not all.
In those countries you can't discriminate something for a public job based only in their university, this would be also illegal. Any degree of type "X" emited by a valid institution must de accepted if you ask for an degree of type "X". All are equivalent. In many fields, physicians for example, you can't work without a degree. But you can work as physician in UK with a Spanish or Chinese degree for example, because this is regulated. Private companies of course can lie themselves in any way as they want. Is their money after all.
Your reality may be different.
> You cannot directly conclude anything based on the graduate's degree grade
If your candidate show a CS degree, you can directly conclude that this people have skills related with computer science, and related with having a CS degree. You don't know if he/she is able to drive a truck, this is true.
> or individual scores
Also standardized.
> Without eg. the institution where they studied.
Information casually written in big fat letters in the CS degree.