If your Pokemon evolves later it could learn more attacks in its pre-evolved form that maybe could not learn if evolved (particularly true with Pokemon who evolve from stones) or it could skip some attacks that should learn in its evolved form.
In this case, it is not important, because butterfree will learn Confusion at level 12.
Caterpie evolves into Metapod, starting at level 7, then Metapod can evolve into Butterfree at level 10.
I don't know what a Meatpod is. However mETApod evolves into Butterfree at level 10.
Metapod evolves into Butterfree at Level 10.
Metapod evolves into Butterfree at level 10.
Caterpie evolves into a Metapod, Which then turns into a Butterfree at level 10.
Kakuna doesn't evolve into butterfree, it evolves into beedrill at level 10 METAPOD evolves into butterfree at level 10
Caterpie evolves into Metapod, starting at level 7, then Metapod can evolve into Butterfree at level 10.
It evolves into butterfree at level 10
Caterpie evolves into Metapod at level 7. Metapod evolves into Butterfree at level 10.
I don't know what a Meatpod is. However mETApod evolves into Butterfree at level 10.
At level 10 Metapod evolves into Butterfree
Metapod evolves into Butterfree starting at level 10!
Metapod evolves into Butterfree at Level 10.
Metapod evolves into a Butterfree at level 10.
Metapod evolves at level 10 into Butterfree.
Metapod evolves into Butterfree at level 10.
Caterpie evolves into Metapod at level 7 and Metapod evolves into butterfree at level 10