Aged coffee is a thing. I tried something in the 10-15yo range once, and for a dark roast it wasn't bad.
I have gotten some nice aged coffees, an aged Sumatra and a monsooned Malabar (they age it in a warehouse open to the monsoon wind and moisture).
But these were aged while green and I roasted them fresh.
I wonder if what you got was something more like that, aged green and then roasted after aging?
It was a natural process roast that got me to even care about the difference, and now I almost always go out of my way for light roasts.
If you’re in/near/visit Seattle or have access to any of these roasters: Seattle Coffee Works specializes in light roasts, most of Victrola’s single origins are light, and many of Ladro’s are as well. All three often have at least one natural process. They’re all quite good!