I'm using Airdrop to transfer application internal data between two phones. Because Airdrop was intended for file sharing, it could occur that user choose "save the file" to save the data file in Files app by accident. Since my app is a financial planning app, I'm considering to encrypt the file transferred by Airdrop to keep user's data secure. The encryption only applies to the temp file transferred by Airdrop. Once the app on the receiver phone receivers it, it decrypts the file immediately.

I'm referring to this

Assuming that you use AES from Apple's Crypto Kit framework, the second clause would apply. You don't need to provide any documentation to Apple but you should submit a self classification report to the us government.

The exemptions you listed in your question do not apply since you wouldn't use a symmetric cipher with a key length of 64 or 56 bits.