If they're going to put a Moss Rock and Ice Rock in Johto, they'll have to be in separate, inaccessible rooms from the normal areas you can visit before the Elite Four.The reason is that the way this kind of evolution works is that it checks the location data for the map you're on. So in other words, Eevee will evolve into Leafeon no matter what area of Eterna Forest it levels up in, not just the patch of grass in front of the Moss Rock. This means that the areas with the rocks/magnetism will have to be blocked off until later (on a different map).
Like if they required Rock Climb, or if an NPC blocked the way, or if a new path mysteriously appeared out of nowhere (think Spring Path in D/P).
Of course, if they put them in Kanto, it won't matter.
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