There is a difference between USER changeable vs. being set at the aircraft factory. Yes, SOMEONE has to be able to enter the speeds for a given airplane, but that does not mean the end user will be able to change them.
As far as the Grand Rapids thing goes, that, pretty much by definition, means the end user can change the settings because it is designed for, and marketed to, the experimental crowd.
Again, no direct knowledge. But it seems that someone besides the factory can change the setting then so would the owner. With Garmin that might be a bad assumption.
And yes, GRT settings are all open even if factory installed, S-LSA