Yea... I didn't say that. Getting a custom bike means you're getting a bike made specifically for you and your needs. A good custom builder should know enough about geometry to figure out how to cook up a frame that fits the customer's needs. Someone who's good at bike fitting might not necessarily be good at or know how to build a frame, but a good custom builder should know a good amount about frame geometry.

The keyword is "good", which also happens to be very objective.

I don't know anything about geometry, and I'm not picky enough to go out and commission a custom job for the sake of geometry. All I know is that I have long legs and a short torso with normal arms.