Polynomial-over-normalisation conjecture for the expectation value

Let $F_L$ be the expectation value defined from the two-boundary Temperley–Lieb ground-state eigenvectors, and let $Z_L$ be the corresponding normalisation. Let $P$ denote a polynomial in the model parameters. Polynomial-over-normalisation conjecture. The expectation value has the form

$$F_L=\frac{P}{Z_L}.$$

Equivalently, its numerator contains a factor $Z_L$, which cancels one of the two factors $Z_L$ in the defining denominator. This is a structural claim about the finite-size expectation values, but the supplied text gives no proof or resolution.