I was a fire inspector in my previous life. If the Cause was electrical and the origin was a receptacle, then the receptacle was to blame.
If I determine that bad wiring at the receptacle was the cause, then the dummy who last touched it, is to blame.
But that would require the fire inspector bringing in the EI (or another qualified person) and consulting with him to confirm such findings.
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If an insurance company read the report written by the investigator (only done 50% or less) they might be able to assign blame.
I don't know how the insurance companies handle it internally, but I know they higher private investigators to determine cause and origin a lot. Those guys may, or may not have a clue as to what they are looking at electrically.
The labeling "electrical" does not damn the last electrician that touched it, at least not from a criminal court of law perspective. I can establish a reasonable doubt that I was the last one to touch is as an electrician. Since I was not in the home every day to watch over the HO, who knows what they did.
In civil court, the preponderance of evidence is easier to make it look like the last EC was at fault, but the Fire Investigators report, if properly written and detailed enough with the EI consult, would refute that, if you were not at fault, or it would put you on the hook
