tells you can claim a draw by threefold rep. But does not tell you how to do it.
There is a chance that the other lad too did know the threefold rep rule.
Between them they have played 314 games with only 7 draws.
The OP was involved in a 3 fold rep before, Game 7482613
but it may not have been him who claimed it or perhaps it was just agreed.
(His opponent in that game 'kqnbrp' has played 149 games with only
3 draws so there is a chance he too was not aware of the 3 fold rep rule.)