The lift of the tail,
$$ L_t = C_L.q.S_t $$
The moment of the tail around c.g.
$$ M_(cg,t) = C_M.q.S.c $$
look at the S in the two equations.
Why the lift of the tail is proportional to the surface of the tail while the moment of the tail about c.g. is proportional to the surface of the wing ?
If I consider the moment of the tail as the tail lift multiplied by the arm, then the moment will be independent of S, the surface of the wing.