I've now run the stats with roads that have no associated addresses removed.
This looks substantially better, the total number of objects in the GWR has gone slightly down because obviously the issue even existed in the old data just not as bad.
To make things easier to understand the per municipality numbers http://qa.poole.ch/ch-roads/ "all" link now actually contains all objects indicating if they were removed because of the filtering, as you will see from the data it seems to be a bit of a per canton by canton issue.
GWR OSM (matched)
2017 2019 2019
Corrected
Streets 125'781 158'272 131'299 107'962
Points 2'374 1'918 1'615 N/A
Areas 25'025 55'079 47'883 N/A
None 34'700 7'989 4'880 N/A
Total 187'880 223'258 185'677 131'116 (+ 3'855 with minor spelling differences)
See https://wiki.openstreetmap.org/wiki/OSM_-_GWR_Street_and_Place_Names_Compari... for explanations.