Sorry mate but that doesn't make sense (to me) for a couple of reasons:
1. How can you make this statement when you haven't tried a bunch of different bridges (material/construction) on your guitar? I can't pick exactly what is affecting what on any of my guitars (body wood/type, neck wood/type, fb wood, pickups, tuners, bridge, scale length etc) because no 2 guitars are the same, and I very rarely change a component on a guitar and record the differences, plus my memory for nuances of tone doesn't extend past how long it takes me to change a component.
Fair enough, but I'm a credential led player and I know my own ear. I personally think a 2 Piece bridge or a string through variant could be more resonant. I'm basing this on experience of ownership. I do notice nuances if they are there, I don't trick myself into things. I can hear if a pickup swap was pointless for example, or if an all mahogany guitar is up against a maple cap. One doesn't always need to record to hear differences.
2. By definition of resonance, you're making a false statement. If the bridge is "bright", then it is adding resonance in the "higher" frequencies.
What a lot of people mean by resonance, is the vibrations that get through the body. Surely you'd understand that? The SC I have now is not particularly buzzy or sustainy. This feeling is pleasing to most players and often comes with a nicer woody tone.
Aluminium is also used a lot because it's highly conductive and forms a protective oxide layer. Both materials work harden though, but all of that means stuff all when talking guitar bridges. Harder? Heavier? Does that mean "better"?
More expensive? Yes, and also harder to machine, but why assume PRS is compromising on cost here?
Because it's what businesses do. The bridge of the terms used to be all brass, if they are still I don't know. Brass is better for vibrations and sustain but costs more. I have a Yamaha with a mahoosive all brass bridge tailpiece, it sounds epic.
As for "aluminium" vs "aluminum", both spellings are accepted, and "aluminum" even more so being a US guitar/site. I think "aluminum" sounds funny, but that's because I'm Australian.