Do the sakura biomes just not exist? Im in java fabric 1.21.5 with the most recent Terrestria version and the logs are in creative but says the biome doesnt exist?

The Sakura biome is off by default because Mojang added a competing biome (Cherry Grove). You can turn it back on in Terrestria's biome config file.

(Now I've answered this question in all three places you cross-posted this question. ;)