I'm intrigued as to why they didn't use a big.LITTLE design (or whatever they're calling it these days). Perhaps mainstream-linux still isn't so great at handling it.

Really the only benefit of that is energy efficiency if it is used correctly, in exchange for additional cost or lower max performance. Makes sense for a smartphone, less so for a mains powered device (and the Raspberry Pi SoCs originally were designed for set-top boxes, although I don't know if that's still true for the new ones or if they're custom)

energy efficiency also leads to higher sustained clock speeds if your not using a fan to move air over a heatsink