Wrote a number of these sonnets. As in the example linked, the final line was in iambic heptameter. There was something hauntinly beautiful about the sequence. I’m can’t remember if it had a name or not; but strangely, I remember a line in one of them concluding with the words “apple core.”
I believe you will find that work in her “Sonnets From An Ungrafted Tree”, my dear.
Aha! so it is! I do remember the title now. You do have so much of our beloved “chaff” packed tightly in your brain! I’m not sure what prompted me to use this Millay closing line, however I do like the sound, It begs a sequence be written using that technique.