my understanding was that this was not actually a settled topic, and there was ongoing debate as to whether or not they were thermochemical structures, with the main evidence against them being "basically temperature features" the fact that they're not a classic plume shape
However, further imaging work seems to show that 1) they actually do seem to be a classic plume shape in many cases (or, more precisely, have complex shapes compatible with convection), and 2) most do have temperature anomalies associated with them. Some things we thought were plume related may not be, but folks are much more in agreement that they look a lot more like convection-related features.
E.g. compare these two papers (which are both basically review papers): https://www.sciencedirect.com/science/article/abs/pii/S00128... https://www.nature.com/articles/s43017-021-00168-6