but this would of led to higher fuel burn
Not if you read the Lycoming manufacturers data.
The SFC on the "higher powered" injected models for the same HP is lower.
The O360 J2A is "derated" only with the line on the MAP gauge and the MGB limitations.
Read Ray Prouty's sections on "design tradeoffs" - they are a lot different to what you portray as the issue.
Its all about picking yourself up by your shoelaces!!