Natural Bias of FMN switch to bound state

Should FMN switch dot plots be biased towards bound state? This paper suggests the answer may be yes.…

And further it suggests as I have maintained—

“The average
observed melting point ™ calculated from the two-state
folding transition of each measurable nucleotide (see
‘Materials and Methods’ section) slightly increased upon
ligand binding [average Tm±standard deviation (SD)]:
64.9±4.6 C (unbound) and 69.3±4.3 C (FMN bound)”—

melting point should go up when bound, or at least not go down.