You generally don't get technical interview performance feedback because technical interviews are constrained by the interviewer to put themselves in a technically confident light against the candidate. The interview is as much a crapshoot for the interviewer, because they might be less/more/similarly skilled to the candidate, but they absolutely cannot reveal themselves to be less skilled because they would undermin…
I try to use it early in the interview, and I find it sets a helpful tone, avoiding a lot of that posturing you describe.