A YouTuber named DirtyTesla has done a series of drives over the years throughout his hometown where he's tracked the intervention and disengagement rates per mile. He often shows those numbers at the end of his videos.
I think that is not true. They can just take data from the route, annotate it and put it into their training set. That is how you would do route tuning.
Sort of off-topic but I believe Openpilot allows this. You can record every route you take, copy it off to your PC and run it in a simulator. You can then tweak the model for this particular issue.
If not, they might take harder and harder routes as FSD gets better. Making it look like there is less progress than there really is.