No way to remove keys from keybase keyring

It seems like keybase can decrypt encrypted messages without even a passphrase. It makes me think keybase is storing the passphrase or stripping it. In any case, it seems like it is fully removing this layer of protection!

So I generated a pgp key with gpg --gen-key and gave it a passphrase.

Then I imported it into keybase with:

keybase pgp import -i ~/.gnupg/secring.gpg

Then I tried encrypting and decrypting a file:

gpg --armor -e -r MY_KEY -i ~/Temp/test.txt
keybase pgp decrypt -i ~/Temp/test.txt.asc

Now I just press enter directly without entering a passphrase, and it does:

Please enter your Keybase passphrase to unlock the secret key for:
PGP key Lingliang Zhang <lingliangz@gmail.com> A6FEE68AAB1BBE34

Reason: PGP Decryption: 
▶ WARNING error unlocking key: Input canceled
SECRET DATA HERE!!!!

Somehow it is able to decrypt without the passphrase? The same behavior using gpg just give an:

gpg: Invalid passphrase; please try again ...

This makes me wonder, is keybase stripping the passphrase before importing the key? How is this possible?

Start by reproducing the import and decryption flow with gpg --gen-key, keybase pgp import, and keybase pgp decrypt, including the canceled passphrase prompt. Compare the behavior with gpg and determine whether the imported key retains passphrase protection; done means the cause is documented and the reported key-removal or protection behavior is addressed.