I've read that boruto has lightning and water release. I know he used the arm machine thing but how does he has them. I never seen him use the elements without the tech
He just never trusted in his own powers during the exams, even though he was actually strong. He was too afraid of failure to rely on his own strength, and also didn't appreciate the value of winning through his own power and effort.
After the exams, Boruto's only "fight" was against Momoshiki, so there wasn't really a chance for him to show off his own powers.
Well clearly. Even Sasuke pointed out that he used one of the three elemental natures in his Rasengan (which most likely is Wind).
Anyway:
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So unless he is lying about the fact he can make shadow clones, and if Sasuke is also lying about the Vanishing Rasengan ...Then most likely the boasts about his talent are justified.