Ah, yes, that. Yea, not explained at all, I think they just felt it was cool ;)

Here's the thing, if we're to get pessimistic (that is, look at everything from the boring perspective of "character motivations" and so on), Qui-Gon's a huge dumbshit for launching at Maul without waiting for his partner. Once again, we get to wonder why they can't just remove those shield generator thingies with the Force.

But yes, the way it's filmed and conveyed, that meditation scene is bloody cool. And a good piece of characterization if taken for itself (Maul is arrogant and certain of his superiority, Jinn... well, he's arrogant before and after this scene for not waiting for his partner, but in this scene, he's thoughtful, reserved and aware of his physical inferiority... I guess).