Just as disappointed as you.
Anyone that wants to help, the guys over at xda are putting in work: https://forum.xda-developers.com/t/cant-unlock-bootloader-failed-to-unlock-your-device-please-try-ag.... I've been able to follow most of the conversation. Suffice it to say we may need to reverse engineer this bid to get it to work.
If anyone is seeing this post that HAS an unlocked/rooted Zenfone 8, they sure could use your help. The rest of us will either have to wait for an unofficial (read: risky) unlock tool, or for Asus to actually live up to their promises.