What does the 'Foundations Starter Kit' mean for arena?

Hello everyone! Even if i'm an old magic player, I'm relatively new to Arena, and the spoiler of the Foundations Starter Kit made me confused. Well what really made me confused was reading this: "a starter kit for the set featuring nearly 400 cards, all of which are legal in standard but many of which aren't available in the main Foundations set!"

What does this even mean for card acquisition in arena? That there are a bunch of cards not available from the packs that you can only craft with wildcards? (ofc if you are new to arena, otherwise you could possibly have the cards as they are reprints)

Thank you to anyone clarifying this! ^_^