We have not (but I’m sure that they’re very busy, and it’s at least a moderately complex protocol to review). Do you know if there are other cryptographers within the Zcash community who might also be interested in offering feedback? I think we might want to wait for the ECC regardless, since many of our revisions and alterations to the original proposal were in response to their first round of (really excellent) feedback, but feedback from others could be helpful as well.
Perhaps it’s a good topic to raise with other projects who might be interested in doing shielded airdrops, since I expect that the mechanisms required would often look similar (at least for any Zerocash-style commitment/nullifier privacy schemes, a broad category which includes Aleo, Anoma, Aztec, Penumbra, Namada, etc. etc.).