Found this morning that the acceptance note for this process is a hybrid acceptance/solicitation and is sent to two poets. Weird, but very cool to write:
Dear Poet X2: I am building an audio anthology of contemporary poems online called Whale Sound, which takes submissions. Whale Sound recently began accepting submissions made on behalf of third-party poets. Poet X1, copied above, saw and loved your poem ‘Z’ (available online at link Y) and suggested it to me. I loved it in my turn and am asking for your permission to interpret it for Whale Sound. If you have a moment to visit the site, you will get a good sense of my style and approach. Please let me know if this works for you.
(Thanks to Whale Sound poet Laura Sheahen for this submission!)