[perlgeek]

It seems the reasoning here is: the TLS handshake might have used an insecure TLS version, and so they cannot be sure that the handshake worked the way they thought, and so the certificates could have been issued to the wrong party.

I don't have a deep understanding of the TLS-ALPN-01 validation nor of the vulnerabilities they might be concerned about, but that would be the only reason for revoking certificates (unless it's more of a political statement, "we revoke certs when we screwed up!").