Actually, Pilot-br, If I am to understand your translation correctly this is normal, and, as far as I know, the way clearances are issued all over the world.
An ATC clearance is a somewhat "fluid" authorization, in that it is expected that amendments occur enroute , and for the approach phase. This is necessary because it is impossible for the issuing controller to know in advance, or even with prior coordination, what the next controller along requires, and the next, and the next...
In our ATC manual, and I expect, all others, a clearance is defined in this manner.
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Said this before in this thread, I'll say it again, thousands of flights are cleared, daily, at initial levels that are subsequently amended enroute for various reasons, including fuel efficiency as the aircraft burns fuel off and wants to climb, unavailability of existing level due other traffic, weather, and quadrantal rule (the case here.)
From what I've learned of this accident, I believe it is more an equipment issue, too.
When the transponder return was no longer received by ATC, the symbol-which is not large, nor I imagine particularly attention grabbing - changed. That was the clue available to the controller/s. Against that clue, the information in the datablock reverts not to the last assigned ATC level (370) but to the flight planned level (360). A counter-clue.And, in human factors terms, a deadly one. In addition, the radar system used in Brazil triangulates the position of the aircraft and offers an approximate level, which is displayed. This displayed level, at the crucial time, was also 360.
So yes, there are things the controllers might have noticed, and perhaps should have done, particularly when communications were interrupted, but I for one can easily understand, given the incorrect clues displayed, why the controllers might have believed that the flight was at 360. Had any controller had doubts about this, and no communication with the aircraft, they would have made darned sure the Gol aircraft was moved laterally away from the flight path of the Legacy.