My understanding was that the challenge wasn't in getting things "right", it was in introducing parallelism in a way that didn't negatively impact core performa

My understanding was that the challenge wasn't in getting things "right", it was in introducing parallelism in a way that didn't negatively impact core performance. In other words, they didn't want to go back. Though, OCaml is also not purely functional - I don't know to what degree OCaml's various escape hatches would have hindered multicore. All the text I've seen is about avoiding regression.