Why do the character have to use the specific skill/ability listed on the conflict to Help one another? Is it too gamebreaking to let the characters help one another with different skills/abilities if they can justify it?
Stay cool 
I don’t have a full answer, but remember that the GM gets to pick one extra skill that’s helpful as well.
I remember a lot of what the book calls reaching in conflicts in MG. In conflicts, everyone is really, really keen on helping with every single action, sometimes going to ridiculous lengths. I like the restriction; it’s faster in play and makes conflicts a bit more challenging and risky.
According to “Helping in Conflicts” (p. 72) you can only help if you “have the ability or skill listed for the current action” or, failing that, I Am Wise.
Yup!
This is exacttly it. You can read it p.30 Suggested Help, there is also a reminder in the Ability and Skill Factors p.136.
Oops. Missed the part about being in a Conflict.
So… what Bobo said.
And Nature.