I disagree. Of course you may be right
No, ATCwatcher, you mix up procedural control with a Flight Level Allocation system, which is not the same.
Procedural control is applied where radar is absent. Under procedural control any level may be used in accordance with the semicircular system. Flightplanning is similar in both radar-based and procedural systems. ATC interventions to provide separation are also similar. Strict adherance to the flightplan during flight is never the case, impossible in fact as I have argued.
A Flight Level Allocation System as a method to strategically separate aircraft may be applied both in procedural as well as in radar control.
Aviadornovado may indeed have thought of FL allocation in his reasoning. FL allocation is indeed a method to strategically separate aircraft, in order to reduce the need and workload for tactical separation by the controller. As far as I've understood (but here I stand for correction since you have followed the Brazilian collision and its aftermath much closer) FLAS was not the case in Brazil.
In the Amazonas it looks indeed like the application of procedural control for those parts of the flights going through non-radar areas. Nothing wrong with that. Any region out of radar range where ADS is not yet applied is controlled in this manner. E.g Northern North Sea until the day of today and indeed south-eastern Europe, not only Greece, in the 70s. In those days the Austrians had to bear the brunt over Villach VOR where for eastbound traffic the longitudonal separation had to be changed from some 10 NM radar to 10 or 15 minutes procedural. The difficulties of this changeover from a radar based area in western Europe to procedural control for traffic to the southeast led to Flight Level allocation in that area, and also to Flow Control which was later organised and improved to present-day Flow Management by the CMFU in Europe.
This brings me to say that "new" ATC-overloaded areas like Brazil and India are in dire need of a Flow Management System to safely cope with their problems.