Is sustaining vote needed for full-time missionary serving in a district AUX presidency?

We have a senior couple missionary called to District (in the mission) YM presidency. Does this particular missionary need to be presented to local members for a sustaining vote? Or is this a case of just announcing him as a FYI item for local members?

Handbook 1:4.9.4 ("Missionaries in Branch Leadership Positions") is not very clear on this specific question.

Good question. Part of me says that it shouldn't be necessary for the reasons outlined for setting apart. But the legalistic side of me says that in the absence of any direction to the contrary, they must still be sustained.

Also, if we go by the assumption that whatever we choose will be wrong, I'd rather error by sustaining someone who didn't need it rather than error by skipping it.

Of course, this comes with the usual disclaimer: The local leaders hold the keys to interpret the Handbook. If they have questions, they should ask their presiding authority.