Some users have recently had their accounts hijacked. It seems that the now defunct EVGA forums might have compromised your password there and seems many are using the same PW here. We would suggest you UPDATE YOUR PASSWORD and TURN ON 2FA for your account here to further secure it. None of the compromised accounts had 2FA turned on.
Once you have enabled 2FA, your account will be updated soon to show a badge, letting other members know that you use 2FA to protect your account. This should be beneficial for everyone that uses FSFT.
Maybe this is just pointing out the obvious, but I'm guessing the one in the second link (model ending in -NRSN) is just an older revision of the same drive. The specs look the same between the two, and the only thing I can find about the -NRSN drive on the WD website is documentation from August 2010. The -HLHX drive, on the other hand, is all over the WD website, so I'm guessing it's the current revision, which might explain why it's more expensive than the -NRSN drive even though the -NRSN is retail and the -HLHX is OEM.
If you really want to know the exact differences you might want to contact WD directly.