Because I know the ropes (I was undergrad advisor for many years)
I get the cumulative GPAs of those among my students who have them
(some are new students). After I assign my grades I always cross
check to see how concordant I am. If I think I've missed by too
much In a reasonably large class (N>100) I assume a statistical
universe and I set my average grade for those with CGPAs at their
average grade. Excel gives me easy ways to analyze things.
I'm quite sure that if the Registrar knew I was doing this he
would change the output of one of his reports to omit the CGPAs,
but he doesn't. I also have a "backdoor" method for getting
enrolment updates. Though the Registrar refuses to update our
class rolls on a daily basis, his system does update my class
mailing list automatically, and I, as the owner of the list, can
download their ids. With a bit of work I assemble a concordance
between my roll and the email ids and I've got the information I
want that he doesn't want me to have.
It gives me great pleasure to subvert whatever I think to be
unreasonable, and I've found no shortage of targets in my 33
years of university teaching.