World creation isn't random, it's based on the seed.
So as long as Chunkbase uses the same world generation algorythm as MC it can figure out where everything will generate.
But it has to use the correct algorythm for the version of MC you're running.
You say your world was started in Alpha, have you updated the game? I guess so, otherwise you wouldn't have any jungles if they were added later.
If it's updated to a version with a different algorythm then the world will be a mixture of of the two (or more), areas that were explored in an earlier version (or that are close to explored areas) would have been generated by that version and areas explored in later versions generated by those versions.
So parts of Chunkbase's map should look like your world and parts wouldn't.
You should set Chunkbase for the version you are running now and find a jungle that's outside the area you have explored and that should be where Chunkbase shows it even if the areas you pass on the way don't.