This is true. The best representation of Wyverns in comparison to Dragons in Minecraft is Ice and Fire Dragons vs the Mo'Creatures' wyverns. Both start out at basically the same size, but when the wyvern reaches adult size, it's really tall, with the dragon reaches its full size...that's brown trousers time.
On the topic of other mods, does anyone have any ideas for mods for a modpack, with Ice and Fire being the central mod? A dragon hunter themed modpack if anything.