Ricardo, I am sure, knows that RCT is a method for making an internally valid inference from the sample with which the RCT experiment was done. To extend its findings beyond the sample and the experiment is not statistically valid ---for validation of findings to other contexts would in general require repeating the experiment in each context or embedding all contexts in a super model and use the relevant statistical inference techniques. This is well known and uonderstood, Ricardo should read Section 7e.2 of C.R. Rao.s classic text Linear Statistical Inference.
T. N. Srinivasan is Professor of Economics at Yale University and Research Fellow at the Center for Research on Economic Development and Policy Reform, Stanford University.