Board Thread:Theories and Speculation/@comment-3001903-20160312031728/@comment-2043993-20160323200605

Not unlikely that they used it in some training or test capacity. Fourth Rakage said that he and B used to train there, so it's not unlikely that others did the same.

The turtles' movement isn't necesarily a disadvantage concerning Chunin exams, it just makes the drop-off and extraction a little inconvenient sure, but not using a highly dangerous environment that's at your disposal for training would just make it more of a liability (as in Money sink) than an asset.