What you don't seem to understand is that engine is overloaded just as FC says. That means it can fail.
If it does not fail the first time, it's life is dramatically shortened in comparison to just running the engine at its rated maximum continuous power of +7lbs.
That is why FC dictates the engine is dead-lined, the use of +12lbs entered into the maintenance logs, and the engine must be inspected by a mechanic before it can be returned to service.
If your engine fails in an airplane, their is no re-fly button. It is the pilot life on the line and he only has ONE.
In accidents resulting from engine failure in flight, if the pilot deviated from published operating standards for the engine, it is a factor in the engine failure in
EIGHTY FIVE PERCENT of the engine failures recorded by the FAA.
Let that sink in for a moment.