I think the primary reason we logically conclude True Seeing does NOT in fact negate an entire school of magic is simple:
1)TS is a divination and not an abjuration and therefore not meant to be protection of any kind.
2) There are no similar spells that shut down other schools of magic as entirely as mpl argues. I'm sorry this is a sore issue with you, but sometimes when you stand alone, it's because you are in fact wrong.