Tested for safety? We know what it does. It gives a low dose of the virus. If we know most people will get it anyway, then we don't need to know more than that in terms of either safety or efficacy.
A low dose could trigger an incomplete immune response leading to antibody dependent enhancement (ADE) on exposure to the virus in the future. Other Coronavirus are known to have that characteristic, we dont know if this strain does. Safety is making sure that we aren't priming people to get worse versions of the disease like what unfortunately happened with dengue.
Of the 79 infected, 19 died. E block (where the index patient was), had 53 infections and 15 deaths for a mortality rate of 28%. Other units had 26 infections and 4 deaths, for a mortality rate of 15%. The death rate of patients in E7 (closest to the index patient and with the highest viral load) was 70%. That's more than 4x difference in mortality based on viral load!
It would be very surprising if low doses of SARS-CoV-2 caused higher mortality. Therefore should allow researchers and volunteers to experiment with low dose deliberate infection. It could save hundreds of thousands of lives.