I think that was an over-exaggeration.
Devil May Cry Forums
DragonMaster2010
Lain
There was this chart for DMC4 that compared the heights of humans and demons, Dante was around 195cm (6'4 inches) so they gave Vergil that height since they're twins. Also, keep in mind that it's possible that Dante was shorter in 3 due to being younger. But I agree that it's a little silly.
AgentRedgrave
Okay, coulda swore I posted this. But I did find a picture of concept art from the anime. It claims Dante's 190 cm (around 6'3"). Dante and Vergil being tall itself isn't really what I find silly is trying to picture how freaking tall Arkham must be, he towered over both of them in DMC3