ATC Watcher correctly notes:
... the Legacy was flying exactly at the altitude it was set to fly : 37.000 ft, and so was the GOL 737 . Should one of them had an altitude deviation , not even a large one , as it is meant in this WP , they would have missed.
A few decades ago, autopilot and navigation accuracy were "loose" enough that a significant (albeit imperfect) additional layer of separation redundancy existed. Two aircraft on the same route at the same altitude had only a small probability of occupying exactly the same space at the same time. History will never tell us how many near-GOL-1507's happened and went unrecognized.
Autoflight refinement, RVSM, GPS ad inf. have stolen this last slice of the cheese from the aviator's safety net. Two aircraft cleared on the same route at the same altitude have a much higher probability of exchanging paint.