I agree it does look a bit unusual, but the colour might just be a response to the dry conditions. There is another species of Eriochilus whose leaves are purple on the underside, but it grows in shallow soil over rocks more towards the coast. What do you think, Tobias?
Hmm yes not sure. This wouldn't be that other Eriochilus with purple underside, although I wouldn't be surprised if some E cucullatus have some purple underneath. This wouldn't be a Acianthus of some sort by any chance?
The leaf shape doesn't really look like Acianthus, and they usually grow in colonies anyway. This leaf also looks slightly hairy, which Eriochilus can often be, so I'm happy to call it that.