Many of the cheap off-shore sourced wheels don't pass anything. Even if they have markings.
Back in the 60's when you bought wheel blanks, took the centers out of your steel wheels and welded them into the wide blanks you bought out of a magazine, do you think that has any approvals?
DOT replaced ICC. If you thinks of what ICC was about, it might make a little more sense. Interstate Commerce Commission. Regulating commercial traffic between states. It's about commercial traffic. Production vehicles as built by a manufacturer, are often used by businesses. The federal regulations on how safe new cars are built isn't even DOT, it is the FMVSS regs. It is a pretty heafty book covering a ton of safety specs. From braking, and brake system failures and still being able to stop. To window defrost performance.
For private use, most anything goes. Think of all the axle swaps, modified suspensions, etc. Running tires way larger on trucks way heavier than the brake package was ever engineered for. None of this stuff would ever pass any OEM testing, but is run on the street all the time.
Beadlocks unsafe? I've seen more issues with 3-piece wheels separating into 2-piece wheels. The centers unbolting from the rim. Do you ever hear anything about those wheels being illegal? Hint: they are not.
For years there was someone who had a bounty on someone why could actually prove beadlocks were illegal. Never heard of anyone claiming it. Just the urban legend.
Split rims scare me way more. Those are still legal. Just nobody will work on them nor will anyone accept the risk of making new ones. A few places will still work on them, but they are few and far between.
So a beadlock may not have a DOT stamp, where is it required to have a DOT marking on your wheel? There are the high end custom one off wheels churned out on a CNC mill, don't see those with any DOT markings. Nobody complains about them.