BLE long range support
It looks like the MetaMotionS uses the nRF52840 SOC, an upgrade from the nRF52832 used in previous models.
The nRF52840 supports BLE long range. This, among other things, means that you can configure the output power to be 8 dBm.
The MetaMotion API still only allows to use values up to 4 dBm, as required by the nRF52832. This indicates that you may not be considering using BLE long range.
Are you planning on supporting BLE long range for the MetamotionS?
The MMS firmware r1.6.2 supports tx power levels from 4 to 8 dBm, but may need to be enabled in the API.
The PHY mode is set to automatic in the firmware, which allows data rate changes and/or coded (Long Range) modes if requested by the master using a PHY Update request.
At present, advertisements do not make use of coded mode, so the device will need to connect at a closer range first.