I do not recall learning any of these symbols in my Private Pilot training in New England. Maybe they teach this type of thing to Alaskan pilots? but there is nothing in any private pilot curriculum that I have seen that describes these symbols.

I think, that as a private pilot, I would use a big smoky fire with a huge SOS written out somehow near it to get the attention of other private pilots who are not specifically looking for me.

Are Search and Rescue personnel taught these symbols? If they are, and you know a team will be looking for you, then these symbols would probably come in handy, but I'm not sure Joe pilot just doing some sight seeing would know how to interpret them.

My $0.02... I defer to the experts of course.