Hello, let me comment on those matters, because there is a lot that can be said.
so, first of all what you observed about FE_GET_PROPERTY is not (exactly) a bug, because FE_GET_PROPERTY returns the values from the S2API cache and that cache is (usually) set with the tuning parameters that the application software set and not the one detected by the hardware, i.e. the actually tuned parameters after different auto-detections made by the hardware. it could be debated a lot of FE_GET_PROPERTY and what it's supposed to do or what not and how that changes from the initial version of S2API, i.e. Linux DVB API version 5.0 to the current version, but it's pointless, because my understanding about what you need and want to get is achieved using FE_GET_FRONTEND - in fact in reality most likely FE_GET_PROPERTY just falls back to calling FE_GET_FRONTEND anyway. unfortunately, if you 'grep' all existing open-source DVB-S/S2 demodulator drivers in Linux you will see that 'get_frontend' is not implemented at all or there is some "fake" or partial implementation. unfortunately, that applies for the open-source STV090x demodulator driver too, which 6925 driver for Linux uses - we don't make STV090x demodulator driver for Linux and thus 'get_frontend' implementation of it is "as is". however, all DVB-S2 demodulator drivers we developed - for example for TBS 6981, etc have real 'get_frontend' implementation and report back the actual tuned signal parameters obtained from the hardware after the signal lock was acquired and my understanding that's what you want. however, 'get_frontend' is not aware of some S2 parameters and that's why what TBS drivers returns is 'proprietary' format in a sense that you need to know how to parse it to determine some parameters like the detected modulation type of the signal. anyway, in short in the current state of the Linux DVB-S2 drivers (and i'm talking just about the TBS drivers) the closest to what my understanding is you need you can get it with the TBS 6981 driver (and basically all other TBS cards based on NXP demodulator chips like 6984, etc). also, some of the real signal parameters you can get with parsing BBHeader information that 6925 can provide and for which recently i posted some easy-to-use patches for the TBS Linux driver packages here:
http://www.spinics.net/lists/linux-media/msg45597.html