Richie, it is safe to say that if one properly grasps the user manuals, and has a solid understanding of how the features they intend to use on their spark are meant to function they'd be one step safer.
To help insure a safe flight, before taking off make sure of a few things, proper GPS connection for spark, Compass/Imu are Calibrated, and that you take off from a clearing without overhead obstructions.
Then in your settings make sure your RTH height is safely above any obstacles and within legal limits for your area.
When you do take off, keep the spark close by and Verify that the home point has been updated and matches your take off location on the map.
If you did all of that, and your location is looking good on the map, then the sparks return to home should definitely probably work.
There are so many factors that come into play when piloting a drone that relies on wifi and gps, so theres no absolute answer unless the person telling you also flys at the same place you fly at. That along with subtle differences in manufacturing as well as dirty sensors, weather conditions and other variables can throw curve balls at you.
To sum up the rant, if you do your preflight checks, and make sure your homepoint is correct your spark is designed to return to that location. As someone who has done a few range tests and lost connection with my spark, mine did always return home and usually within a foot or two of where it took off.
If you dont need to be standing under the trees while filming, try flying over them at an angle from a clearing, then you can maintain LOS, im sure you may have thought of that though.
