Modern CVR/FDR (black boxes) units are built to withstand 3600g for 6.5 milliseconds, this roughly equates to an impact velocity of 270 kts. In addition to the penetration resistance, static crush, high/low temperature fires, deep sea pressures, sea water immersion and fluid immersion.
FDRs are usually located in the rear of the aircraft, typically in the tail. In this position, the entire front of the
aircraft acts as a "crush zone" to reduce the shock that reaches the recorder. Also, modern FDRs are typically double wrapped, in strong
corrosion-resistant
stainless steel or
titanium, with high-temperature
insulation inside.
Judging by the impacts down through the years that black boxes have remained "exploitable" after, serious question will have to be answered if the "un-exploitable" report is true.