My thought is that, the reason for this rule is for privacy concerns, but then, I might be wrong, so my question is "are there or is there any security issue(s) related to using or reusing a particular or one single bitcoin wallet address for a very long period of time?
Poor privacy leads to a risk to your security.
Let's say you use the same bitcoin address for everything. Now, everyone you have ever bought, sold, traded, spent, earned, swapped, or otherwise transacted bitcoin with can see every transaction you have ever made and can see exactly how many coins you are holding at all times. Do you really want every single person you have ever interacted with to be able to see exactly how much you are holding? What if one of them decides that you are holding a bit too much coin and decides to help "relieve" you of some of it. Or maybe they tell one of their friends. Or maybe because they also reuse the same address for everything, someone you've never met who they have also transacted with starts to track you down. Because you were careless with your privacy, you make yourself a target for attacks.
In general, the entire list has some pretty big flaws.
The majority of users should never even look at their private keys: Just write down your seed phrase and be done with it.
Doing ID checks/KYC with multiple different buyers/seller is a fast track to having your identity sold on the dark web.
You shouldn't forget your private keys because you shouldn't have remembered them in the first place. Just write down your seed phrase.