IIRC, the BMA/6 "certification" evolved from a Consumer Products Safety Commission's 1970s attempt to try to protect children from Dangerous Things. I think the thought was, if bicycles for kids are made less dangerous - i.e., less prone to component failure - kids will suffer fewer injuries. So the CPSC took standards from the Bicycle Manufacturer's Association re: frame & component stress testing etc, & awarded "certification" for "children's" bikes of such quality. Schwinn & other manufacturers of "adult" bikes weren't a concern for the CPSC at the time.
Biggest thing I remember (as a teen, when this BMA/6 certification first appeared in '72 or '73) was all the stupid reflectors that began sprouting on the newly "certified" bikes. I think, if memory serves, that the BMA/6 standard called for simply reflectors rather than headlights or taillights - lights were probably more effective for safety, but not necessary because kids obviously wouldn't be riding bikes at night anyhow!