1. DL and UL DTX are both working independently. You can activate one of them, or both.
While UL DTX is ON, the UL timeslots contain no power when there is silence. But DL timeslots are sent with power.
There is no link between them : I can talk (UL), or you can talk (DL), or you can remain silent while I’m talking, etc. Each direction is totally independent.