We’ve learned a lot more about the risks of these test since 1985, particularly with Kessler’s paper "Collisional cascading: The limits of population growth in low Earth orbit" in 1991. The implications are much better understood now. Plus alternative test regimes, such as the tests in lower orbits, have shown that tests at this altitude just aren’t necessary. It seems highly unlikely that there’s much about this system that couldn’t have been tested just fine against a safer target.