This is semantics. My fault for not explaining fully in the above reply.
If an ECAF arbiter incorrectly rules on a case and orders the reappropriation of funds to another party, then it effectively interferes with the immutability of the blockchain. Yes, the blockchain code isn’t reversed in any way, but the outcome – the result the person who thought they had sent an immutable transaction in the first place - is being modified (by the arbiter) after being created, therefore the intended result becomes mutable.
RE: Proposal for an incremental Constitution and Dapp layer governance on EOS