One thing to think about is even though you may have enough data centers to cover ~+100 progress, when setting the floor progress the game takes into account the total progress, before any reductions. Eventually, the total progress (before reductions) will be high enough that the floor (lowest) AI progress is raised, and at that point if your effective progress (total - reduction) is calculated to be lower then the floor, it will remain at the value of the floor. If this does not sound familiar, i suggest you read the tool-tip by hovering over the AI Progress meter, and also the tool-tip for SuperTerminals.
Hope that helps!