Beware that it is not just the Finnair A320 fleet that is seeing these new seats rolling out. Their A321 fleet will also have them by the end of August.

Following some feedback I gave to Finnair they told me about how environmentally sound this new seating configuration was and then went on to say "The installation of the lighter seats will continue during summer and is planned be completed in all Airbus A320 and A321 aircraft by the end of August.". So I'm guessing that these will soon be across the entire fleet.