Thanks Nigel, On ADS-B it is often hard to tell what has actually happened.
Sometimes they must power up the aircraft and tow it over closer to the hanger in preparation for departure. It is not uncommon to then see the aircraft again on ADS-B when it actually departs, maybe 30-60 minutes later. The same would apply for the engine run up you mentioned. Cross checking with FlightAware can be helpful, however many of the US Registered aircraft have their flight details blocked, and this is not possible. Unless you actually see it moving on the map, it is hard to confirm exact movements, and best guess applies.
Can't beat your Eyeball Mk III information, I only have Eyeball Mk II at best.
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