I don’t think changing the “Pattern System” in the prefs does anything. It’s an unfinished feature. I think the idea was a user could select a pattern system, and then in SeamlyMe the user could create an empty set of measurements based on that system? Someone could correct me if I wrong.
The list of known measurements though are a collection of all the pattern systems, some being duplicate measurements with different names.
That said, In my opinion the pref should be removed until it’s fully implemented as it’s just a confusing red herring at the moment. It’s like a web site with the proverbial fais pas “Under Construction” that never goes away.