It's already pretty common knowledge for tree care in general, there's nothing specific about this for swings. Already ever major town or city around the country has an arborist or team of arborists to make sure trees don't randomly fall on people and kill them, and the way they do that is by using either this test or else just manually coring the tree by cutting out a tiny section to check for rot.

If you as an individual want to own trees, and especially if you want to let others use your property, I don't see any reason why you should be held to a lesser standard of care than any municipality across the country. If you can't afford to keep your trees safe then you can't afford the trees and/or the property.

But yeah, this definitely isn't anything beyond what you'd learn in a plant pathology 101 class in college or a basic arborist certification.