Certain features are not SUPPOSED to be in a limited feature radio (P5100, P5300, M5100, M5300) but they CAN be purchased for the radio. However, those features may (possibly) be sold to you for that radio only if you pay the cost difference between the x100 and x300 models.
Depending on the radio in question, the difference may ONLY be in software OR there may be hardware differences as well.
For example, an M7300 mobile radio is a 700/800 MHz radio with available GPS and it will support P25 Phase II TDMA operation, and OpenSky and OpenSky2.
But an M5300 is 800 MHz only which is not listed as supporting Phase II TDMA or OpenSky2.
However, my M5300 HAS the Phase II TDMA option in it.
The difference is software. The radio chassis is the same for an M5300 and an M7300 in the same band. I am presuming that the GPS option is installable in the M5300 even if it's not formally listed for that model radio. (Which I don't know one way or the other.)
Oddly enough, while I have Phase II TDMA in both my P7300 and my M5300, I don't have P25 (phase 1) trunking in the M5300. This happened due to a mistake made when I ordered a P25 upgrade.
I asked for P25 Phase 1 and got Phase 2 instead. I've kept it but will eventually also go back and get Phase 1 ordered for it.