None of those studies involves eliminating kidney stones in patients who have them. One study was in vitro only, not in humans. Another study involved a grand total of one person. Another one enrolled 12 people, still not enough for anywhere near conclusive evidence that lemon juice significantly inhibits stone formation. And the fourth study (from Turkey) looked at urinary citrate and uric acid values but said nothing about forming or treating kidney stones.
We don’t generally “fear” quackery. Laugh at it or shake our heads in disgust is more like it.