I am a neophyte with ADS-B and FR24, so I guard myself against taking it too seriously. That said, ADS-B provided to me by an authoritative source with respect to a recent accident, though not truly conclusive, certainly triggered a worthwhile discussion about what the airplane was doing just before an inflight breakup. And, knowing [roughly] where and when for the in flight breakup (because the output stopped) was useful. That said, two more recent test flights I made were picked up by someone on FR24 as having been two minutes duration each. That is not actuate. So my trust in that information is not entirely certain.
But, with accident investigation, you consider everything you have, and then how credible it is, and how it fits in with the rest of what you have....