Steven doesn't say anything that is 100% about Hoenn protagonists. No proof at all. Events from gens 1, 2 and 4 are 100% confirmed to have already happened before B/W, while only R/S/E events are not even mentioned. Why?
Where is that confirmation? "Travel through time" can mean as well that R/S/E take place after B/W and B2/W2. It's not said if Pokemon arrived from past or future.
Anyway, this message about travel through time is shown only for Pokemon transfered from GBA games. Pokemon transfered from R/S remakes won't have this message anymore, so there is no proof at all.
This timeline discussion is for another thread, so if you have any other ideas to prove I'm wrong about timeline, post them in appropriate thread.