User blog comment:Omega64/Boosted Gear Sub-Species Ideas/@comment-87.2.71.229-20161114125249/@comment-29963364-20161114172329

As explained in the Sacred Gear page, and mentioned by Vali in vol.21:

Tobio had already achieved the Canis Lycaon's Balance Breaker, [Celestial Night Slash Dogs], when he was born (he's one of the very few cases where that happens).

After mastering his Balance Breaker, he trained to refine it even further, and eventually reached the "Abyss" of his Sacred Gear. The end result was him literally "becoming one" with his Sacred Gear.

Also, the DxD does make the armor "organic", but that only applies to the armor itself, not Issei or Vali. It seems like when Ophis used her blessing to help Issei and Vali unlock the DxD, her blessing caused the armor to turn into "flesh & blood" bodies for Ddraig and Albion.