What is really happening
Underdense trails produce very short bursts; denser trails can persist longer. Modern timed digital protocols assemble an exchange from multiple valid bursts.
Do not confuse it with this
A single partial decode is not a completed contact, and random calling without synchronized periods can make two stations transmit over each other.
Use it deliberately
Synchronize clocks, use the accepted sequence and frequency, aim for the path geometry, keep frequency stable, and complete every required exchange element before logging.
Operating shorthand and propagation models are tools for making a better decision, not proof of a path, contact, or safety condition. Confirm with current rules, measured signals, weather, and the complete station.