Nah, based on panel 4 their sizes seem about in line with official averages. Haxorus are 5'11"/1.8 m tall and Pelliper are 3'11"/1.2 m tall. The rub is the body shape of Pelliper being long and wide in addition to the actual standing height.
Basically, Pelliper are much bigger than you think they are. And I'm now remembering youtube videos entitled "Pokémon sizes are NONSENSE"
Nah, based on panel 4 their sizes seem about in line with official averages. Haxorus are 5'11"/1.8 m