I found a flaw in the security.
Any app installed in Secure Folder is supposed to be separate from the rest of your phone / world. I use Signal installed inside Secure Folder and on my Note 8 no messages show any text, it merely alerts me to a message but says that it's private.
BUT, while wearing my Gear S3, the text of the Signal message comes through completely. I've not tested it on other smart devices, but I imagine it would do the same.
This would be an easy way to compromise a supposedly secure folder/app. I can, of course, turn off notifications for that app, but NOTHING is supposed to exit unless you give it permission.
One can only wonder how many other apps may communicate "protected data" through the Secure Folder.