To be fair, the US has been developing and testing tailless designs (for future supersonic fighter applications) since at least the 1990s.
The most visible examples being the Bird of Prey and X-36.
Based on what we've witnessed, it's
plausible or
arguably more likely than not that China has since surpassed the US in this domain, as it has in other areas like HGVs and MaRVs, in part due to years of DoD
misprioritizations.
However,
unless you have access to highly classified data from SAC, CAC, Lockheed, Northrop and Boeing on the current states of their tailless efforts, we ought to
maintain an open mind and a measure of humility until enough information emerges to allow for a reasonably comprehensive comparison of next gen Chinese and American tailless designs.