That was my point, that if you hold the tube with you facing the sun then it is too bright and the dot is much more visible and you will measure a falsely low CYA reading. Telling someone to stand facing North in the Southern Hemisphere will have them facing more towards the sun (depends on how far south and what time of year). South Carolina is well north of the Equator so the sun most of the year is not directly overhead but is from southwest to southeast so in a southernly direction. Taylor saying to face North is clearly advice specific to the Northern Hemisphere. I think telling people to just have your back to the sun is best since that is fairly consistent indirect lighting, is independent of hemisphere, time of day, etc.
So a flashlight pointed to the side of the tube sounds like it gives you consistently accurate results so that is another method, but I would not tell anyone to face the sun and take a reading with strong sunlight directly entering the tube. Lighting does matter. The fact that you found something equivalent to outdoor indirect light by using a flashlight is great, but doesn't change the fact that you can't ignore the amount of light (nor its direction) one uses for the test.
So a flashlight pointed to the side of the tube sounds like it gives you consistently accurate results so that is another method, but I would not tell anyone to face the sun and take a reading with strong sunlight directly entering the tube. Lighting does matter. The fact that you found something equivalent to outdoor indirect light by using a flashlight is great, but doesn't change the fact that you can't ignore the amount of light (nor its direction) one uses for the test.
