Hirschowitz's formal principle conjecture for smooth unbendable rational curves

Let $A$ be a smooth unbendable rational curve in a complex manifold $X$. The curve $A$ satisfies the formal principle: whenever a compact complex submanifold $\widetilde{A}$ in a complex manifold $\widetilde{X}$ admits a formal isomorphism

$$\psi:(A/X)_{\infty}\stackrel{\cong}{\longrightarrow}(\widetilde{A}/\widetilde{X})_{\infty},$$

there are neighborhoods $U$ of $A$ in $X$ and $\widetilde{U}$ of $\widetilde{A}$ in $\widetilde{X}$ and a biholomorphic map $\Psi:U\stackrel{\cong}{\longrightarrow}\widetilde{U}$ such that $\Psi(A)=\widetilde{A}$. Hirschowitz's formal principle conjecture. A smooth unbendable rational curve satisfies the formal principle. This is presented as a special case of Hirschowitz's conjecture on the formal principle; the supplied text does not state whether it has been resolved.