I had an iPhone and an MacBook both on iCloud and keychain synced.
I then logged out from iCloud on both, wiped them and sold them.
I then bought a new iPhone and MacBook and logged in to my iCloud account, used the same passcode on my devices and all my keychain data was still there!
According to Apples documentation the keychain should be wiped off the servers when all devices logout.
(I had two Apple TVs logged in to my account the whole time, but they don’t have access to the keychain from what I understand).
