Hi Lampogolovii ^^/
I assume you mean you bought the main Sprout Lands Asset pack since I uploaded this UI one yesterday.
In that case, no the UI pack is a separate extension pack to the main Sprout Lands pack and is not included with the main pack. Therefore yes you will need to buy it separately.
I would love to give all my pixel art assets away for free, but I also really want to build up a living where I can sustain myself in creating art and game material. hope you understand ^^
Let me know if I miss understood your question, I would love to help :>