I think the bottom line is that anybody flying a carburreted engine, with their fairly standard mismatch of fuel distribution, and without a multicylinder EGT/CHT instrument, is flying with hands tied behind their back as far as getting optimal economy, and they have to play it very safe, and they need to fly full rich a lot of the time when somebody else with the proper kit can operate optimally.
An accurate fuel flowmeter is a huge asset but not for engine management as such; it enables you to fly long trips with confidence, and if necessary make intelligent diversion decisions well ahead of time.