I have been running Sony MDR-1ABT with LDAC for a long time, but I used them with the Xperia Z3 that did not have LDAC. So I bought the Xperia XZ1 and I also got the SONY WH-H800 headphones with LDAC as part of the promotional event.
For the first few days I used my old MDR-1ABT and I could choose an LDAC codec with priority on audio quality or connection stability. Then I paired the phone with the new WH-H800 and the possibility of connecting LDAC devices and selecting connection priority disappeared. (I do not know if it was related to pairing new headphones, updating, I do not know ..) After a few days, the option to select LDAC returned again with the option of setting the connection priority - it worked for both earphones models. Now it disappeared again. I called to XPERIA support (Czech Republic) but could not help me.