Monotonicity conjecture for the inconstructible-polyomino ratio

Let $P(n)$ be the number of polyominoes with $n$ cells. A polyomino is constructible if it is the concatenation of two polyominoes of smaller sizes, and inconstructible otherwise; let $Q(n)$ denote the number of inconstructible polyominoes with $n$ cells. Inconstructible-polyomino ratio conjecture. The sequence

$$\frac{Q(n)}{P(n)}$$

is decreasing. This conjecture is based on the available values of the sequences, computed up to $n=56$ in the source. Its resolution would provide the conjectural monotonicity needed for the paper's conditional upper-bound discussion, but no proof or disproof is given.