Because this pack is no longer sold, any NSP you find is technically unsupported. Ensure your source has proper "proof" screenshots showing the 12,000 Tokens in the top right corner of the menu.
The Ultimate Pack is distinguished by its exclusive racing suits, which are not available for purchase with standard currency.
: These credits grant access to the premium tier of seasonal rewards (battle passes). Exclusive Cosmetics Founding Member Suits & Liveries
Disney Speedstorm Ultimate Founder's Pack: The Definitive Guide
The is not a separate game or DLC NSP file . It's a digital entitlement (a license flag) that unlocks specific starter content within the base game.