What results does the magnetic dating method yield using 607 instead of 586? How does it falsify 607?
The initial assertion in this thread that the method 'confirms 586' was a misrepresentation of the source material, so your question isn't really valid.
Aside from that, the discrepancy between secular history and Watch Tower Society dogma doesn't remain at 20 years, but diverges to a difference of 68 years at the beginning of the Divided Kingdom.
Using the new dating method, they were able to confirm the destruction of four sites by Hazael around 830 BCE, but Watch Tower Society chronology requires that those events happened around 890 BCE. The method also determined that a fifth site was likely associated with an attack by Shoshenq "70-100 years" before 830 BCE (consistent with my reckoning of that event in 925 BCE), though Watch Tower Society chronology would require that that happened in 993 BCE. (Also note that the range of "70-100" years indicates a margin of error that renders inconsequential the selection of 586 instead of 587 for the fall of Jerusalem for their purposes.)
Additionally, the dating method confirmed that parts of Judea remained populated until decades after the destruction of Jerusalem, which contradicts the superstitious hyperbole that all of Judea was desolated for the entire period.