xerxes
ようこそ!ワタシの音楽工場へへへへへ
The former can't be true, since I see people on the internet shiny hunt through DexNav all the time. Unless you mean DexNav chaining starts with an elevated shiny chance
It means that DexNav chaining doesn't actually increase the shiny rate per x chains, like the Pokéradar did for example. The odds are always the same but better than regular encounters. Like MMing.