Question about mashups

I want to upload a Spotify mix on TikTok. Before, i used to add one of the two mashed up songs as a sound and set the volume so low (to about 1%) so it becomes inaudible

Now I realized other creators have (Original by: their profile/ contains: one of the two mashed up songs). But when i upload i get that the sound is by me and no reference to any of the songs

How do they do this? Also is it better to have it this way or not? I just wanted any of the songs referred to get the algorithm push