why does donger's turrets health have scaling scaling?

it scales like this: 125 + (25 × level) (+ 「 5 / 8.5 / 12 / 15.5 / 19 / 22.5 / 26 / 29.5 / 33 / 36.5 / 40% of Heimerdinger's AP 」

is it just me or is it wierd to have scaling ap scaling on a skill? i guess it's to make his earlygame weak and late strong, but his turrets are already weak in the lane..

was this tested or just an experiment to see how it would work out?

PS: yes i realize riot won't buff donger since his winrate is so high in soloQ.