Someone correct me if I’m wrong, but it looks like there are two hashes. A short one based on the iCloud account’s email address or phone number, and a long 2048-bit RSA identity that gets stored on the device after logging into iCloud.
It looks like the short identity is basically just used for that initial airdrop screen where you find available targets to airdrop to, but the actual longer, more secure, hash is required for the actual file transfer.
That might explain why finding airdrop contacts is kind of snappy, but there is a bit of a delay after you initiate a transfer.
Edit: one more thought. If this really was that easy to crack, wouldn’t China have done this years ago? The CCP has been targeting Airdrop for a long long time.