No true. Thermal updrafts and downdrafts was a big feature of SU9. Asobo brought it up in at least 3 Q&A videos (and provided video demonstrations) but didn’t mention it in the patch notes. That’s where they messed up. They should have provided a clear explanation with the release of SU9. The casual gamers would have still complained, but at least there would be a little less confusion about why their plane is moving around on days with high thermal turbulence.
The system is based on the simulated sun intensity, which heats the ground, which results in updrafts and downdrafts (thermal turbulence). The sun intensity is dynamically calculated based on your location, time of year and time of day. The sim samples spots on the ground all the way out to the horizon and then uses the sun intensity to simulate heating the ground\scenery based on the terrain and whether or not there is shade.
Based on my tests, it does not seem to be based on temperature, but the “intensity” of the sun on the given time of day, time of year, and location. So live weather doesn’t play a big role, outside of potentially creating clouds that shade the terrain, which results in less ground heating. This is all part of what Asobo calls their atmospheric flow engine. It’s one big system that tries to simulate all the dynamics of Earth’s atmosphere, allowing for native simulation of gliders without having to use weird workarounds like randomly placed thermals.