That is part of the problem with any analysis of what could have happened.
We don't know for sure if all the input is correct as reported. The old garbage in garbage out.
We don't know if the background checks (some of which are complete some which various countries haven't even released yet) have issues. Everything is speculation based on fuzzy information.
All we know is what is reported and we don't know how much of it is actually correct. Which is what your comment illustrates ""turn off time" is inaccurately quoted".
If there was an electrical fire maybe it disabled the telemetry system before the last radio comm without them knowing? I don't know all the systems on the plane and what the possibility is of an electrical fire going unnoticed for ~12 minutes. That's my only guess for why the transponder was turned off before last radio comm IF we assume this article/post's point of view is correct.