Although Amazon is somewhat stereotyped, the name in itself is missleading. The Amazon is indeed one part of the country, a huge part, but the bonus of the ability applies to all rainforest, and Brazil has developed on the coast, where there is a biome called Mata Atlântica (
https://en.wikipedia.org/wiki/Atlantic_Forest) and that is, in game, mainly rainforest, as rainforests in game represents tropical forest overall. That fits the way Brazil has developed, and the choice we need to make in game, of chopping or not the rainforests, getting the production for chops or keep the adjancies bonuses. I like the idea behind the UA, though I think Brazil could be way better if we got it later, not Vanilla (like the Ottomans, that many felt a huge gap and now everyone is thinking it is a good OP civ, at least for Dom).