Because that can change. Often. We hardly know what the lowest level possible is for a lot of them, because we didn't go through HGSS as thoroughly. We can guess, but then someone finds it lower. It's best to just leave it as references on the wild Pokémon and move relearner page.
Move relearner moves are just the level-up learnset. Moves "exclusive" to the relearner are just moves from a lower-than-legit level. You could hack an encounter with a wild Sceptile at level 22. It'd have Absorb, Quick Attack, X-Scissor, and Pursuit, in that order. But you can't get wild Sceptile, and Grovyle doesn't evolve until 36. That's why it's "exclusive".
All I ask for is just a tiny bit of understanding of how the games work when you look at the wiki. Figure at least some things out yourself by playing.