Going back to the OP and Garmin's pothole warning thingy. As above I switched it off because I found it distracting, but I still look at the warnings on the map. But gradually the whole of the UK road network is being covered with pothole warnings, beginning with areas popular with cyclists. So the prevalence of warnings doesn't mean more potholes, it just means more cyclists with Garmins reporting potholes. It's a kind of heat map but focusing on cyclists who use this feature.
Here's a view of the Surrey Hills.
View attachment 771279
Aggregated, there are 17 reports around Peaslake and 14 around Box Hill. Are these particularly holey areas? No I don't think they are. There are holes, yes, but there are holes bloody everywhere.