when deck adjustments and even tire pressure will make a difference in actual height numbers may not be exact (on mine I measured right from the dealer for a benchmark) - but a number that is close is a lot easier for me than a letter that means nothing to me ,or worse my wife, so we can come close to what we are shooting for. and with not indication on the decal if it is inches or an arbitrary number most people will not find it worth it to go the manufactures home state to file the suit.
I used to work at a womens prison and the prisoners were raking in the dollars scamming old retires as they knew the people had to come to our county to sue - we did all we could to clue people in but saw many loose a great deal of money. with a business it is handled in district civil court too and not small claims so the rules are different (MIL is a retired atty for the state)