I'm confused by a statement in https://bitcoin.org/en/developer-guide#hardened-keys
"For this reason, the chain code part of an extended public key should be better secured than standard public keys"
I'm confused because I thought the chain code was an intrinsic and easily deciphered part of an extended public key. For example the top answer here explains how to derive the chain code from any extended public key:
So how exactly is one supposed to obey the advice from bitcoin.org to "secure" this chain code when it's openly exposed in the public key itself? Does a "hardened" public key not likewise expose its chain code?