It should be Omelette! Haha
"My phone is running Android 8.1.1 Oatmeal Cookie" is just too awkward.
"My phone is running on Android 8.1.1 Omelette" is like, fine.
Oreo already rejected that request a few months back
Your guess is as good as mine here. Regardless, I am interested in a preinstalled handset with the pending OS in question.