Good grief. A lot of assumptions, some poorly conceived marketing hype, and we have bad information. The MA bearings are simply the same material used in darn near every new car - - the ones that will go hundreds of thousands of miles with minimal wear. It's an aluminum alloy on a steel backing. The alloy has a bit of silicon in the mix, somewhat similar to a hypereutectic piston. The silicon adds hardness and wear resistance to the otherwise soft aluminum. They ( the manufacturing facilities both aftermarket and OEM) like aluminum bearings because it helps remove lead from the products and the plants, and satisfies EPA regulators.
The upsides to aluminum as a bearing material have always been low cost, resistance to snagging/sticking to the crank, and environmentals. The downsides have been fatigue resistance and wear. The silicon and alloy development have addressed those weaknesses and made it into a good bearing choice. The hard material will not embed debris like an old soft bearing - hence some marketing wordsmith thought it would be an advantage to state that they would polish a crank in service - making the hardness an advantage instead of a disadvantage. When I left F-M a decade or so ago, aluminum was considered satisfactory for clean environments (passenger cars and light trucks) with power levels up to perhaps a hundred horsepower per liter. I am certain that given the time and advances in technology, that those levels have gone way up.
I still prefer a multilayer bearing (Clevite has a trademark on the term "Tri-metal") for my builds - and want a 1/2 groove or 3/4 groove design, but a street guy won't be in trouble with an aluminum bearing from an alloy perspective.