No, they were not careful about their claims. Putting aside the drama around the arxiv postings, they had previously explicitly made the "discovered a room temperature ambient pressure superconductor" claim in a Korean language journal, in a 2020 submission to Nature that was rejected, and on multiple patent applications.
There is no evidence of them doing interesting work, either. If reporting is to be believed, their company mostly does unrelated consulting odd-jobs for the chaebols, and this was a passion project for Lee and Kim. But you know what? I'm glad there are oddballs like this on the fringe of science. They're mostly harmless, occasionally entertaining, and maybe once in an epoch they might come up with something real.
There is no evidence of them doing interesting work, either. If reporting is to be believed, their company mostly does unrelated consulting odd-jobs for the chaebols, and this was a passion project for Lee and Kim. But you know what? I'm glad there are oddballs like this on the fringe of science. They're mostly harmless, occasionally entertaining, and maybe once in an epoch they might come up with something real.