"X but for Y" has been around for a good long time, it long predates (and I would say is significantly distinct from) "not X, but Y"
I think they're both "negative parallelism" constructs. Either way, neither are new.
The prose on https://mail.cyberneticforests.com/its-not-just-data-its-pos... changed how I think about it: the framework is useful for reasoning, not lazy writing. This bubbles.town submission's title could be light evidence of negative parallelism's utility. (Or, more likely, just the stochastic nature of what's popular when)
Indulging in meta-commentary: The HN submit history for bubbles.town is interesting. Took 7 tries to reach the front page. The final viral title resembles the supposed-LLM-tell "X not Y." Coincidence or evidence that the models touch on a useful way to communicate ideas. (I only looked because I submitted the one 2 weeks ago.)