The nuclear recoil energy of 248 keV is apparently relatively large compared to expectations. Not 100% sure, but this also seems to imply that for vanilla interactions one would expect more lower-energy events in the same experiment -
For this reason, the researchers seem to invoke a certain type of interaction in their modeling (though not terribly speculative, one of the possible interaction types), a momentum dependent interaction, to suppress events at lower energy.
That could be a slight strike against the observation being a real signal, but this is all me speculating.
The mass of xenon itself is about 130 GeV, so a 250 keV recoil would correspond to a heavy particle doing a strong collision at about a pretty fast for dark matter standards of 300 km/s.