OK, I may have used the wrong acronym. maybe it was IRFB (what the IRB was previously called)
As far as I can find, there is no World Rugby Clarification on this law. I have always understood that approach in the laws means what it means in English... "move towards".
Usually, when the laws use a word to mean something specific, or are using to mean something other than the common English meaning, its in the definitions.. examples
Near: Within one metre.
Receiver: The player in a position to receive the ball if it is knocked or passed back from a lineout.
Touch: The area alongside the field of play that includes the touchlines and beyond.
Maul: A phase of play consisting of a ball-carrier and at least one player from each team, bound together and on their feet.
These all have meanings that are specific to the game.
ETA: OK update. I have found a clarification
"Clarification of the designated members of the Rugby Committee
The Referee’s interpretation in this example was correct. The moment the kicker moves in any direction it is deemed that he is ‘approaching to kick’. The reason for this interpretation is simplicity, otherwise the referee would have to judge when the kicker first moves, and in what direction. It would also be open to misinterpretation by players, match officials and spectators."
It changed last year, and I haven't been keeping up... my bad
Now they just need to define that in the Law... expect to see the change in the 2035 edition of the Laws of the Game!