Resolved an issue where Pokémon sent via Mystery Gift wouldn't be registered to the Pokédex if the game was closed improperly.
It looks like you’re referencing a file name for a update (specifically Version 1.0.2, often labeled as Update 1 in certain communities). Pokemon-Lets-Go-Pikachu-NSP_Update-1___40_1__41...
Here is a quick breakdown of what that update addressed and what you should know about it: Resolved an issue where Pokémon sent via Mystery
This format is used for Nintendo Switch digital packages. In an official capacity, these are handled automatically by the console's firmware. Pokemon-Lets-Go-Pikachu-NSP_Update-1___40_1__41...