I agree with all of the @MI-XC comments above.
The article and comments are too short in their scope. The “it must be this size” idea is flawed. It ignores looking at the specific rider, bike and events.
- A change to a any component mentioned will affect handling AND fit. You can’t decouple the two aspects.
- Rider: Depending on skill, one setup may be better than another for handling and comfort.
- Bike: There are a wide range of current “XC” bikes that may be more like the older style geometry and other new models with more “Down Country” tendencies. That makes a HUGE difference when it comes to selecting component sizes and positions.
- Events: Duration, course profile, trail difficulty and such will all impact what may be “ideal” for the rider/bike combo.
In short, there are no easy answers. No single solution (or mindset) rules all. I have done enough fits to know that every “rule” is meant to be broken. The trick is knowing the right time to break it (or not) 