That prevents more benevolent behavior than it discourages actual malice. As Glorfindel pointed out, it can sometimes be very helpful to write an answer explaining how a duplicate actually pertains to the circumstances given in the question prior to closing it.
That shows the person asking that the community did, in fact, read and understand their question prior to placing it on-hold. Or, at least, it conveys how the community understood the question in the event that the closure needs to be contested.
While it is pretty crummy to swoop in and answer a question then vote to close it as off-topic, I think it's better to leave problematic instances of this as an edge case for moderators to deal with at their discretion than to introduce additional complexity into how the closing system works. As it stands, we'd want to keep the loophole open for duplicates, and if you can start to envision the series of checks involved, you can see how that code would start to smell kind of musty.
If you see chronic or problematic instances of someone actively trying to game the system using this or any other means, just flag the post for mod attention, select "other" and explain what's going on.
This, as suggested, isn't something we can implement because it's not really solving the problem which is already a pretty far edge case to begin with, and it actively prevents more frequent benign use, making it more like a feature than a loophole.
And like I said, if you see someone just copy / pasting answers from a duplicate without doing anything to explain how they pertain to the OP's circumstances, flag that sort of thing right away. But more often than not, people use it responsibly, especially here on meta.