I'll chime in and say I'm a happy shopper. I ordered (12) WD/HGST 10TB HC510 HUH721010AL5201 from bitdeals on 2021/1/27. They showed up on 2021/2/9. They were packaged VERY well. Not Amazon Prime fast but also not Amazon Prime packaging
badblocks just finished running on them (smartctl then badblocks then smartctl) ~8 days later... ZERO issues on all 12. Mine were all manufactured ~ June, 2017 (a few different weeks/batches, so... cool!) so at most a bit over 32,000 hours ago. I'll assume they have about that many hours on them vs. their MTBF of 2.5M hours. Time to copy a whole bunch of data!!
Note: I can't find a way to see POH on these guys from smartctl (connected to an IT mode LSI controller in a Dell R720 connected to a SM JBOD box with SAS2 backplanes/expanders) on TrueNAS Core. Or else they've been wiped as the hours reflect how long they've been powered on since I've received them. But again, I'll just assume 32k, which is what I assumed when buying them.
At this point, I would definitely buy from them again.