No, the HR calls are modulated in GMSK @ 6kb/s approx.
a HR call uses only 1 out of 2 bursts. In other words, it is transmitting only half the time.
HR calls or FR calls in 8PSK is a FUTURE improvement, that is not yet implemented in the GSM networks. The goal would be to keep a high throughput (12kb/s) but be able to place 3 “FR” calls in the timeslot. But let’s wait & see how it is really done.