This doesn't really answer the question of why there's a  there, as if a triumph was earned...

As for it being cheating, I see...it's a "mild" form, as the move is written down to assist your thinking process.  Wait...is that what it does, or does it get you you to stop and consider what you're doing before you blunder??

I don't regard this as cheating.

says Fide Handbook, Laws of Chess :

8.1
In the course of play each player is required to record his own moves and those of his opponent in the correct manner, move after move, as clearly and legibily as possible, in the algebraic notation (See Appendix C), on the scoresheet prescribed for the competition.

     
It is forbidden to write the moves in advance, unless the player is claiming a draw according to Article 9.2, or 9.3 or adjourning a game according to the Guidelines of Adjourned Games point 1.a.

     
A player may reply to his opponent’s move before recording it, if he so wishes. He must record his previous move before making another.

     
Both players must record the offer of a draw on the scoresheet. (See Appendix C.13)

     
If a player is unable to keep score, an assistant, who must be acceptable to the arbiter, may be provided by the player to write the moves. His clock shall be adjusted by the arbiter in an equitable way.

12.4
The scoresheet shall be used only for recording the moves, the times of the clocks, the offers of a draw, and matters relating to a claim and other relevant data.

A promising young junior in California, rated around 1900, used to write down 2 or 3 moves on his scoresheet and then circle the one he ended up playing!  His coach had taught him to do this.  I complained to the TD but the TD told me that since I wasn't his opponent, nothing would be done.

A few rounds later I was paired against him and after a few moves I complained to the TD, who told him that he had to stop doing this.  He blundered a few moves later .

The only things allowed to go on your scoresheet, as far as I'm aware, are the actual moves played in the game, clock times, and draw offers.  That's it; anything else is considered note-taking.

Is it allowed to write down candidate moves on your score sheet (not asking because I'd like to do it, just curious)? I see often people writing the remaining time next to moves, but sometimes also other moves. I imagine writing down whole variations is clearly illegal. Sorry if this is too easy...