I was formerly a customs broker for Amazon in the past and found their orders to usually be pretty typical, usually based around volume/time of year. They definitely rotate vendors based off time of year + what would be seasonally important but I think it's mostly just based off what sells. I don't think their algorithm is quite as complex but I don't think it's any bit weak, honestly. But as I was their broker and didn't work internally, I can't comment to specifics, really.