RE: I Heard That If You Buy...
I think that what your friend meant is DP4 and DP5, the set was split into two mini-sets. Let's take for example DP5 which was split into Moon hunting and Night dashing. The moon hunting booster box came with all 3 different LV.X and the Night dashing came with the other 3 LV.x. So in a way, you did get all the LV.x (all 3 different, no double) in that specific set. But if we are talking about the whole set, which normally we do (eg. DP5: Moon hunting/Night dashing) in order to get the whole set of LV.X (all 6 of them ), you need to buy two boxes, one of each of the half set.
HOWEVER, starting from DP6, they stopped doing the half set thing, and you will not be getting 3 different LV.X in one box. The reprinted charizard and the shining pokemon count as a LV.X. So you will probably get 2 LV.x+ one shining, or 2 LV.x + one charizard, or 3 LV.x, or just 2 LV.x if you're really unlucky lol.
I hope that helps and wasn't too confusing lol