I have since unlocked the bootloader (I think it may of actually came pre-unlocked anyway), rooted and flashed Carbon KitKat ROM onto the phone.
In flashing Carbon I thought that for an XT905, I should of used the unified moto_msm8960 build. However, the install zip starts with an assert to check that the phone is correct for the ROM and thereby has a check (with others) for "scorpion_mini". But, my phone was returning "scorpion_mini_u". So, I editied the install zip to enable it to flash, and it all went smoothly and has been working fine. But, recently I looked at some logs generated by my phone, and it is showing up as msm8960dt; which if I am not mistaken in used by a MOTO X (among others).
So, it would appear that my Motorola RAZR M thinks it is not a scorpion_mini but a scorpion_mini_u, and it also thinks its a Moto X (msm8960dt ), but is "happy" to run a moto_msm8960 ROM, instead of an msm8960dt ROM.
I guess my questions are:
1. Has anyone else come across the above mix of identities? and understands whats going on?
2. Although the ROM appears to be running well, should I really only be flashing the "dt" ROMS onto my phone? either way, it does NOT match the available options in the assert statement for either ROMs.