Defect condition for mixed Shimura varieties and weakly special subvarieties

Let $X$ be a mixed Shimura variety, and let $A\subseteq B\subseteq X$ be subvarieties. Write $\langle A\rangle$ and $\langle B\rangle$ for their smallest special subvarieties and $\langle A\rangle_{\rm geo}$ and $\langle B\rangle_{\rm geo}$ for their smallest weakly special subvarieties. Define

$$\delta(A)=\dim\langle A\rangle-\dim A, \qquad \delta_{\rm geo}(A)=\dim\langle A\rangle_{\rm geo}-\dim A.$$

Defect condition. Every mixed Shimura variety, and every weakly special subvariety, has the defect condition. The supplied span does not give the formal definition of the defect condition or state whether this claim is open, so the precise intended assertion requires checking against the surrounding source.