The major flaw of the BIA measurement is its reliance on population averages when converting resistance/impedance to body water and from there to lean mass and from there to fat mass. I have worked with several such devices in different research projects and the results were only reasonably decent on a group level, not on the level of the individual. But if you are happy with your device that's fine. And you are right, nice to have a natural experiment. Let's see in a few years, how it turns out.