Looking more closely at the inboard brake that Duragrouch is concerned about getting contaminated, I think they did it to better protect the brake disc during folded transport.

To me, the probability of them getting hit and bent during folded transit is more likely than it getting ruined from contamination.

Dahon engineers took their calculated risk, and most likely with more knowledge of failure mode frequency than we've got. (through warranty claims & dealer/shop conversations)

Pix on this page: https://usa.dahon.com/products/hemin...45074858868925