Sold phone but forgot to reset

I sold a an iPhone on eBay recently and I forgot to reset it.

I’ve been through the steps to remotely erase the device through Find My, then remove from iCloud but it’s now saying that it won’t be removed until next month and the buyer is saying it’s been erased but still locked to my apple account.

From what I read it should be immediately able to be set up by the new owner. Have I missed something?