Hello,
I believe earlier releases do have counter for MT SMS connections on SDCCH i.e. C191.
In my case, MC191 is showing no values that is cause of degraded E2ECSSR. Same time, C191 do show values and replacing MC191 makes E2ECSSR fine.
In your case, MC191 must be showing some values.
You are right that normal values for E2ECSSR is 92-94%.
Regards,
FR