  The latest results on baryon acoustic oscillations from DESI (Dark Energy
Spectroscopic Instrument), when combined with cosmic microwave background and
supernova data, show indications of a deviation from a cosmological constant in
favour of evolving dark energy. Use of a pivot scale for the equation of state
$w$ shows that this evidence is concentrated in the derivative of $w$ rather
than its mean offset from $-1$, indicating a new cosmic coincidence where the
mean equation of state matches that of the $\Lambda$CDM model precisely in the
region probed by the observations. An equivalent way to express this is to say
that the dark energy hits the maximum value that it will ever achieve within
the observed window. We argue that conclusions on dark energy evolution are
strongly driven by the assumed parameter priors and that this coincidence,
which we are naming the PhantomX coincidence (where X stands for crossing), may
be a signature of this.
