Swamps generating where savanna's should be

Using chunkbase.com to read the seed I locate savanna biomes but there are always swamps where they should be. I have searched 4000 blocks of the world and I can't find a single savanna, but an unusual number of swamps. My world is attached. Is this an issue with chunkbase, my seed, 1.13 or some other issue and how can I fix it so savannas generate in my world?