Matthew
That doesn't mean they're unsafe, nor uncertifiable.
Sounds good but,
if you don't go at least through a certification process, if you don't test a product according to the latest test conditions and latest stand of knowledge, if you don't have a wide and meaningful documentation
how you could be know if a product is safe or unsafe?
Tragically now we know the problems with this part. Sure it's cheaper to have no STC, but anyone have to pay...