OK, in this case you are duplicating a block which contains a reference (link) to another Object. By duplicating the block, the linked object itself is not duplicated. Think of it as writing https://anytype.io and copy pasting that: you ar le duplicating the link, not the website. I haven’t searched yet, but I’m quite sure there are topics requesting a clearer distinction between block and object actions.
If you open the object and then use the three dots at the top right, you’ll find a duplicate option there, too.
@XxxBalCion does that provide the information you need to close this topic?