It seems to me that this is not about using TRV as another temperature sensor…
Here, people are probably more interested in performing an action using such a trigger.
Therefore, such high speed and precision of temperature indication is not necessary.
A good example of the problem is @cnt.luc post, yes, his situation is from a minority group, but…
https://forum.ewelink.cc/t/trv-zigbee-thermostatic-radiator-valve-implementation-of-scene-functions-for-correct-control/
If the TRV notices that its temperature is xyz, turn on or close the valve, which is exactly what it does locally as a stand-alone device. It’s just missing from the scene as a trigger. If it is not possible to implement a variable for temperature, at least read the valve’s closed or open position and perform the trigger based on it. This still seems like a useful feature to implement imho.
Yes, it can be done using a separate temperature sensor as a trigger, but if someone has, say, 10 TRVs, they must buy 10 sensors to have the functionality that is theoretically already in the device.
There are also other ways to extract live information about the device without interfering with it. I did it in two ways: Reading the value in ewelink and PageProbe in the web browser + webhook or ewelink app and macrodroid observing the application for the keyword and reacting accordingly. Both work but are not convenient for the average user to implement and require a dedicated device.
Apparently the TRV trigger will be available later this year… time will tell.