The thing is,as someone said,it's lenght,not height!In the case of Pokémon with solid,not-stretched body,it's height;but in case of long,serpent-like Pokémon,it's lenght!Put a Milotic or any serpent Poké stretched like a line,and they'll have the height that Pokédex says.

Now,Wailord may refer also as Lenght,not height,but Wailord is actually based on the Blue Whale(Only height,not weight).In my book comparisions,Blue Whales are not only very long,but also VERY huge!Of course they're far bigger than Wailord seems to be,but as far as comparision goes,it's done well.

So,this 'Dex is taking the total-stretched size,and not the actual height.If a Gyarados goes to sleep,it'd curl itself up,and wouldn't be bigger than you.It should take in count the grossor of the body...Comparing to the game,this'dex is kinda OK,but some Pokés are stretched-up too much,like Milotic.However,most pokés with solid body are like in the game meassurements.

XD,Sabdshrew!Mess-up...But the mess-up I hate is Mawhile...Now,about Mawile,since I saw him,I looked at his true face,not the jaws.I though,so cute and so menacing,and that's why I like him a lot now!