Is the interior of Venus dry due to a Mega-collision?

It is claimed that the interior of Venus is comparatively dry since even though it is hotter than Earth its rocks are estimated to be stronger, rather than weaker; i.e. there is more water in the interior of Earth to weaken rocks. The high strength of Venus' near surface rocks is argued from slow relaxation of craters and the high correlation between topography and gravity. How is it that Venus' interior is much drier than Earth? The final stage of planetary formation involves impacting of planetary embryos. The leading idea for Earth-Moon formation involves a large glancing impact. Mars is also proposed to have suffered a major collision. I propose that Venus is dry since it formed through an even larger head-on collision of two nearly equal proto-planets. Both bodies would have been totally disrupted though numerical simulations demonstrate that head-on collisions produce no satellites. The disruption would mix iron and water allowing rapid reactions, releasing hydrogen from the water. At low pressures it would be released to hydrogen gas which would be light enough to escape the assembling planet, and possibly released to iron hydride at very high pressures which would sink to the core. As a result the silicate part of the final assembled planet would be virtually devoid of water. A simple test will be to search for hydrated minerals on the surface of Venus, which are predicted to be stable if they exist. If this hypothesis is correct they should be rare.