Stealth isn’t exactly defined by radar absorption and absolutely isn’t dependent on build materials. The most critical aspect of a stealth design is its ability to deflect. As it turns out, this is largely done through shapes. Avoidance of parallel lines, angles, etc. are ways of reducing your radar cross section (RCS). In most cases, black ball paint coatings or more modern absorbent paints are used in stealth aircraft. However, the material of an airframe or fuselage has absolutely nothing to do with an aircraft’s RCS, it is entirely shape and surface dependent in regards to radar.
The Ho 229 was found to have an extremely efficient shape regarding how it deflected radar, so efficient that the flying wing became the basis for the F-117 and B-2. The Ho 229 absolutely did have a lower RCS than comparable aircraft. That being said, it wasn’t exactly built for this purpose. However, to say the Ho-229 had no stealthy features due to its construction material, would be incorrect.