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The old one should not be so free spinning. The new one has grease in the bearings and therefore provides some initial resistance. Mine was exactly the same, and was smooth and quiet once the engine was running. My idler pulley was the same.
I bought a replacement Belt tensioner pulley just because I replaced the harmonic balancer pulley and idler pulley. Turns out it was a defective piece of garbage from the start. It makes a weird noise for 2 to 3 minutes and then runs quiet after that. I think all the replacement parts are the cheapest crap money can produce and are farmed out to China to manufacture. Here is a screen shot from the Amazon review I left and another guys. Although this is a different brand, most are just garbage
They give us COVID-19 and cheap replacement parts!
IMO, for many parts, OEMs are the way to go. At least with OEM you KNOW the factory designs them to go at least as long as the warranty. Sure, you may get a lifetime warranty on a Duralast part, but I don't want to be tearing the car down once/year to use my lifetime warranty!