Luffy is higher than Kurapika and shorter than Kuroro (both SHF same size despite 2cm difference after timeskip). Gon was shorter than Killua at the beginning but he grew up to almost same height so their difference is not that obvious later. Tamashii made them both 135mm. Leorio will be 17+cm, taller than other shonen jump MCs, which is good.

Some anime and manga shots can depict Gon and Killua shorter than they are, that's simple animation or mangaka error and it happens all the time with different anime/manga. Height of characters is official info, Tamashii has to work with that, and not imagination of some overseas nerd.