The only people who will conform to DIN standards are the manufacturers.
Suppliers only pass on what they receive from the manufacturer and thereby quote DIN standards passed to them.
They probably do not even know what they mean.
The DIN ‘Norm’ is a very large volume indeed and covers every screw thread and finish possible so that the makers can create a commonality products.
Materials and composition are all listed.
Dimensions of tooling and anything connected. Tolereances are listed.
It is an excellent reference but I only ever referred to it a few times in ten years.
The fact that a manufacturer quotes his product to DIN standard should be enough for a purchaser to have confidence in that product.
Mainly European manufacturers, but I doubt Chinese or other manufacturers will use it.
If a product is found faulty then the recourse is through the supplier and normally it will be replaced.
Clive