A bit combative with someone answering your questions.
The area rule was a concept, but there was no way to actually test it out because supersonic wind tunnels were not available until 1951. The XF-91 developed in 1946, so it would not have had the advantage of the area rule design validations.
In August 1952, the first YF-102 was NOT able to achieve Mach 1 (0.98) in the tunnel and Whitcomb redesigned it using the area rule, and in October 1953, the YF-102A hit supersonic.
In January 1954, the flight test on the original was done by the Air Force and in level flight was only able to achieve 0.98 Mach, confirming the wind tunnel tests.
These are from Hansen, Engineer in Charge, and "Nasa's Contributions to Engineering"