Show me a case where a 95% was an F. STEM courses are hard. There is nearly always going to be a wide distribution of scores. You don’t see such glaring differences in non-STEM classes, because, frankly, they are easier to do a passable job on. I have not seen any artificially imposed situation where a STEM student who scored well was pushed down to an unfair or unreasonable grade to meet some kind of quota. This is a straw man.
As far as arbitrarily assigning grades, can you really say with a straight face that STEM grading is more subjective than humanities grading?