Essentially, if the total fee is more than is needed after selecting the two fee paying pre-mix inputs in order to perform a coinjoin, instead of enrolling three post-mix inputs as usual the coordinator will now enroll additional post-mix inputs. This makes the coinjoin transactions larger and therefore even harder to break, as well as increasing the throughput of remixes meaning everyone gets more free remixes faster, all for no additional cost to the users.
Wouldn't this in theory also increase fees a lot for coinjoins?
If we have another ''ordinals tsunami'' like we did recently I doubt this will be usable for most people, except maybe for big whales, but they would also experience big delays.
I am more interested in mixing and privacy in second-layer and I heard about one interesting project is coming out soon, or even better to introduce privacy on protocol level for bitcoin (but that probably won't happen any time soon).