The old style stock rear springs for America were softer than today's stock springs.
These were Mitsubishi part number 4140A319 up to mid 2014.
Then came 4140A466 up to the beginning of model year 2017.
After that came Mitsubishi number 4140A467. All above see thread "Suspension history".
In Europe different rear springs were used, and these were and are also very soft. The change in type number was made in Europe in 12/2015.
There are several makes of rear stock springs available here in Europe.
These include:
CS Germany: Part number 14.620.034
KYB Europe: RA5070
Lesjöfors: 4259271
TRISCAN: 875042108
In the Philipines, KYB RZ5121 rear springs are sold, which should be similar to the
European KYB RA5070. These supposedly being the slightly stiffer sort.
Why KYB have different numbers in different markets beats me.