This is a neat design, but, does this not just shift the issue of trust as to whether the proxy and the target are colluding:

> However, each of these guarantees relies on one fundamental property — that the proxy and the target servers do not collude. So long as there is no collusion, an attacker succeeds only if both the proxy and target are compromised.

I'm not sure how an end user would be expected to assess this any more than they could ascertain whether any particular DoH/DoT provider is as trustworthy as they claim.