Being in the fastener industry I can say that the motor industry are shit hot on spec. There has been a big change in spec with the removal of chromium 6 from the effluent process (watch Erin Brockavich or whatever it's called).
There are plenty of alternatives now, but none seem to withstand road salt quite the same.
Yamaha being closer to the source may have found a better solution

The old silver coating on the head bolts is like a ruspert type finish which is zinc flake in an organic "glue" this organic content is what helps.
The fastener suppliers are different to the brake line connections, so it suggests the spec is poor, not just a cheap supplier.
It is the devils own job to deal with the shit that fasteners in this application are thrown, so don't be too harsh, I wouldn't want the job of speccing them