Johto Starters in Emerald?

I've heard that if you fill up you're Pokedex in Emerald then you talk to Prof. Birch and as a reward he gives you a choice of one of the Johto starters. My Dex. is'nt full yet and before I go through all that work I want to know if that's true in the first place.

P.S. DRAGONZ R AWESOME!

I'm nearly postitive it is. But you don't actually need EVERY pokemon. Just the Hoenn dex, I believe. Which doesn't include event-only legends like Jirachi and Deoxys. I'm almost done my dex(just need to find a Chimecho and catch Latios in Ruby), and I'll let you know for certain when I do.

I'm not sure if this is true but my friend told me you get Chimecho in the grass at the top of Mt.Pyre. I havn't tried it yet.