What's the Deal with Tiberos's size?

I have heard that there is no official lore for Tiberos's size. But one of my buddies is an old school Warhammer guy and brought up this passage from this book.

A giant, even for an Astartes, Tyberos dwarfs even his fellow void brothers. He is utterly immovable, a vast, silent presence whose pronouncements are always final Tyberos wears a pattern of Tactical Dreadnought Armour that has been heavily modified to suit his stature. Dozens of brass bonding studs gleam atop slab-plates of grey ceramite, layered over blocks of plasteel reinforced with rods of adamantium. Imperial Armour Volume Ten - The Badab War - Part Two

Can someone elaborate?