The OTS proofs are also verified client-side, so we are not ultimately trusting relays with these. The relay's role in connection with OTS is more like housekeeping, a bit like having relays filter out events that have bad signatures. I think Inkan is pretty well aligned with the idea that the only thing to be trusted is cryptography. The use of blockchains doesn't really seem to contradict that idea. I guess it's debatable whether it's philosophically in line with current Nostr. However that may be, the prize to be had is a cold storage identity, which is a pretty self-sovereign thing to have.