That is true - the not-so-sharp trailing edge tends to soften the effectiveness of the control surface around its center trim position. Forces the air to re-attach aft of the flying surface, rather than smoothly at the TE. That "space" is turbulence and drag.

No need to go nuts on most models. The 1/64 inlay helps you get a crisp straight edge, and provides "ding" protection -- ie, durability along with a fairly crisp edge.

But the molding and near-zero-thickness capability is why composite construction is popular for high performance designs. You simply can not get wood/foam that thin, and expect it to have any structural capability/durability.