sterm randomly? chooses serial port

When I have more than one target connected, the sterm command does not use my selected target's port, it seems to choose alphabetically.

**mbed sterm --baudrate 115200**
Will often just connect to the "other" target even though I did set the target.
**mbed config target NUCLEO_F401RE**
This config should tell the sterm component in the toolchain to use the desired target if I have 2 targets, in my case namely:
**mbedls
DISCO_L475VG_IOT01A[0] | E: | COM18
NUCLEO_F401RE[0] | D: | COM15**

A note: supplying a -m flag to the command gets ignored/not parsed; a separate class of problem, but might just be fixable in a single ticket.