As I understand it, it relates to optimum pitch control which is better in Direct rather Alternate Law, under certain circumstances.
If you do not have slats extended (G+B lost) and have lost 1 elevator (left G lost) the book get you to select L/G down forcing you into Direct Law where the pitch control is better than in Alternate Law without Slats.
FCOM PRO-ABN-29
Extend the landing gear at 200 kt to revert sooner in direct law. This provides, below 200 kt , a better pitch control than in alternate law with one elevator lost and all slats lost.
I assume that pitch control with Slats extended is better than without Slats at 200kts so no need to force the aircraft into Direct Law yet.