[g_p]

It's a good question, and I believe they mean in terms of the epoxy making it harder to get easy access to the chip to do any shenanigans.

It's worth remembering the threat model for U2F tokens (let's set aside PIV, FIDO2, etc for the moment) - if the attacker has physical possession then they're into your account. Game over. As the authentication is to tap the button.

Sure you can add PIN via FIDO2 (then these protections make more sense), but I can't see any particular threat whereby you would be concerned about this threat under normal circumstances.

U2F helps normal (and expert) users resist phishing attacks, credential relaying, and avoid keyloggers etc. It doesn't protect you against in-person physical adversaries who can steal your things, or take them against your will.

The only edge case I can see where this matters more is if a user leaves the token unattended (try not to! Put it on your keyring, though admittedly your backup token probably is at risk a little here) and an attacker can covertly extract the keys and leave it as found, such that the user is unaware. But at that point you are dealing with adversaries in the real world, and most users have already lost at that point (passwords written down, etc.)