Good points! I never thought about the steel cogs munching away at the alloy body. That being said, the cogs on a Record 10 speed and a Super Record 11 speed (I have both) are a mix of titanium cogs and steel cogs. My Record 10 speed is approaching 20 years old and the aluminum free hub body is showing little sign of wear and tear from the steel cogs that are on it, and that bike (Colnago Master) has been ridden a lot. My C60 with BORA WTO45 isn't nearly as old, but the Super Record hub that's on it isn't showing any fatigue from the mix of steel and titanium cogs. When it's time to replace the Super Record cassette, I'm going to be using Chorus cassettes ( I have a few) and they're made of steel.