The "301 NSP link" refers to a specific type of link used in Pokémon Scarlet, which allows players to connect with others and engage in various multiplayer activities. NSP stands for " Nintendo Switch Package," which is a file format used by the Nintendo Switch console.
That’s when the forum post appeared:
Pokémon Scarlet 3.0.1 NSP Link offers an exciting and dynamic gameplay experience. Players are transported to the Paldea region, a vast and vibrant world filled with diverse landscapes, from lush forests to vast deserts. The game's open-world design allows for seamless exploration, enabling players to roam freely and catch Pokémon in their natural habitats. pokemon scarlet 301 nsp link