Got it.
So when I tune my guitar to "A" equal to 454 hz at the 5th fret instead of 440hz, I can tell the others, "I'm not out of tune, I'm just fine in Victoria, Australia."

I'll give you an A for sarcasm, but evidently you have not got it, Mark. The answer arrived at in a school exam has nothing to do with (e.g.) bungee jumping. Its purpose it to find out how well the student can perform the mathematics. So if they are presented with a given, they will be required to use it. It would be the same if they had told to assume the value to be 20m per second, or 90m per second, or any arbitrary value at all.

If student grew up to be scientists and used anything but the true value in calculating the landing of a space shuttle, however, they would indeed be out of tune.