In the ideal world we would have a gadget to read SAT directly.
In the real world there is the little problem of stagnation temperature rise errors which are suppressed to a greater or lesser extent in the design of the gadget.
So long as the error is tested and well known, it matters little other than for non-fancy aircraft where the pilot has to read and interpret an "incorrect" data presentation. With more modern aircraft, the pilot presentation is made "correct" without any pilot effort .. ah, the wonder of computers .. "nothing can go wrong ... go wrong ... go wrong ... go wrong .."