What's the idea?  There's just no need for 6...Na6 in that position, since ...e5 can be played immediately (in many lines of the King's Indian, ...Nb8-a6 is used to prepare ...e7-e5).

I suppose you can argue that it prepares ...c7-c5 without having to sacrifice the pawn, but then 7.Qd2 c5 8.Nge2! and the knight is misplaced on a6.  Black isn't losing or anything, but he'd much rather have that knight on c6 here.  The c5-square (if that's where you want to go after a future x...cxd4 y.Nxd4) is usually not such a good post for a Black knight in the Samisch, as White's already protected e4 with a pawn and the knight can be pushed back rapidly.

I just don't see the point of an early ...Na6 in the Samisch.  It makes more sense when White's already committed to a Benoni structure, or can play ...f7-f5 and ...Nc5 rapidly, with real pressure on e4.