No, that’s not true at all. That comes from people misinterpreting CdA or drag area as reference area because of the word area. CdA is the product of Cd and A, which are drag coefficient and reference area. CdA gives you the overall aerodynamic performance or at least an approximation. A sail or a parachute has a very small cross section but both awful Cd and huge A. Lacking proper reference materials at the moment, the difference in Cd between a cylinder and an airfoil is probably somewhere about 10 times worse. Steel tubes are only going to be in the range of 1/2 to 2/3 the frontal area of a carbon airfoil, not nearly enough to negate the poor Cd of round cross sections.
I asked Variwall to consider making a tunnel tested kammfoil steel down tube for builders who wanted to keep up with modern trends, but they seem to be uninterested in seriously expanding their range. They still have not made proper S3 replacements.