It doesn't work the same way, Hellblazer. The effects of the spells are immaterial - counterspelling prevents the Al'noth from taking the patterns of a spell in the first place, by either undoing them in the same way that they are being made (using the same spell), erasing them as they're being made (catch-all dispel spells), or by providing something equal but opposite (extra countering spells).
GSC is a versatile illusion spell, capable of creating effects so realistic that despite their not actually being real, they can still inflict damage upon their target (Melf's Acid Arrow) by fooling the senses into thinking damage has been inflicted. True Seeing is a spell meant to see through illusions. Ergo, it makes sense that the former could be used to undo the patterns in the Al'Noth created by the latter.
Once a spell is completed (fully cast), it cannot be as easily undone, which is why it has to be dispelled, and fewer tools exist to do so. It's like stitching. If you've a half-done project, someone could readily come by and unpick the stitching. If it's complete, tied off and sealed, even, it becomes somewhat more difficult to undo, and may require specific tools.