A weapon the increases in size by one size category has its mass doubled. A creature that increases in size has its mass octupled, which means its dimensions double in every direction.

For a weapon to double in weight while its appropriate wielder octuples, it requires that either the weapon only increases its length, breadth and width by ~1.2599x or only the length is increased (making it double in length).

If the former is true, then a Colossal Greatsword is only ~12.5992 feet long, which is less than 20% of the smallest possible colossal creatures height. If the latter is true, then the greatsword is 80 feet long and only a few inches wide and less than an inch thick. Surely it would snap and/or bend under its own weight?

Has anyone else noticed this? Has Paizo simply dun goofed?