It is not 5900X, but I have the results of a test I did with 5950X and 5800X interchanged on the same PC, if that helps.
Peak clock does not determine everything in MSFS.
https://forums.flightsimulator.com/t/fps-difference-verification-between-amd-5950x-and-5800x3d-at-haneda-airport-rjtt-34l-straight-out-flight/531349?u=kanadenyan