There are 2 issues.
One is on a 2015 motor the magnets are surface mounted to the rotor with glue. The magnets can have a tendency to break the glue and fly off over 6000 rpm, causing catastrophic motor failure.
Second is Sevcon processing speed. There can be ride through cutouts over 6000 rpms also as the sevcon can not reliably sense the speed of the encoder data.
Good news, if you were to upgrade to a newer bike one day, the danger of spinning the motor over 6000 rpm from magnets is removed, as the motor design is now that of an IPM or internal permanent magnet where the magnets are inserted into the rotor laminations starting in 2016, and in 2017 the shaft got splined and the belt got stronger and the motor controller got more power to quickly take the SR to 164 km/h even without changing the RPM limit.
I know at least one person with a new motor and belt who rides with a 7000 rpm limit and hasn't had a ride through fault, you would need to get a shop like Hollywood Electrics to program that for you and of course it's not recommended and if anything failed it would be out of warranty, but if it's worth it, you get to make that choice.
Test ride a 2017 SR and see if just the 164 km/h works for you before you try to change anything. The 2017 SR will also accelerate hard right to 164 km/h where earlier models would tend to slow down acceleration slightly over 100 km/h like your 2015.