Not entirely true, there are a huge repertoire of compositions which string together multiple compositions flowing from one scale/raga to another under _ragamalika_. [0] The tradition is quite vast and it is only limited by the artist's imagination than the framework itself. Jazz improvisation, especially the coltrane changes were heavily influenced by Indian classical music. [1].
[0] - https://www.youtube.com/watch?v=yqvDbr4snIQ
[1] - https://indiamusicweek.org/files/coltrane.pdf