true .. though a heat treated tempered steel bolt can be found..

I got some marked 8.8 when I fitted the rear rack on my loaded touring bike ..
were still 5x.8mm , with an 8mm hex head (dont know if someone makes allen cap-screws in that alloy.

Brompton's own front wheel motor project seems back-burnered ,
perhaps they cannot find a ROC/PRC supplier that offers the reliable QC of their production
at a price the company wants to pay .