Leshem Yichud

Question

Dear Rabbi, You wrote, "We do not do everything written in Kaballah." But I thought that you wrote that either you or your father had gone to Rav Auerbach and he had said to stay far away from people who don't believe in Kaballah. Now, the noda beyehudah seems to say that leshem yichud is nonsense, so am I allowed to believe that? And if so, doesn't that show that certain parts of kaballah are simply not true? Thank you for helping me with this issue.