Could be a skill issue on the part of the replicators? The russian anime girl scientist had to make a bunch of modifications (and was cursing the orig authors) before she could make her rocks float.
Of course under the assumption that LK-99 is indeed not what has been claimed, I am not completely ruling out that they just failed to reproduce the material. And while I initially said that the LK-99 paper does at least not look like a crackpot paper [1][2] and still think that was not an unreasonable judgment given my complete lack of expertise in the field, just comparing the presentation in this paper and the original LK-99 paper makes me judge the replicators as more competent. But sure, looks can be deceptive.
Honestly I found their account dubious, it’s difficult to believe that a person with a background in molecular biology to have synthesized it especially given that other groups have failed to do so. There are also no affiliations mentioned on their profile.
Falls into the bucket of "specialists can have weird hobbies" element though - i.e. the background to do this is basically "has access to lead oxide, copper and red phosphorous" and "a kiln" - particularly if you dispense with trying to do the vacuum synthesis as that account claimed too (also a point in favor: having random access to dangerous chemicals is sort of something I'd expect out of states with less enforcement of drug synthesis laws).
The mechanism is plausible - if the reaction actually proceeds by driving off the sulfate and substituting in the copper at high temperature, it's entirely possible the vacuum synthesis of the authors is unnecessary (I have in fact had personal experience with trying to replicate a paper where it turned out that a pretty important step was acting as an oxygen-diffusion rate-limiter, and this just...wasn't identified at all by the papers authors).
a nitpick - I think it's more likely that person is he/him. anime is gender and masculinity averse/avoidant so everyone/everything is depicted in girly tone, else they don't exist
