[sbinder]

Perhaps they're referring to this famous objection of financial institutions to TLS 1.3, motivated by them not wanting to update their MitM software needed for compliance: https://mailarchive.ietf.org/arch/msg/tls/CzjJB1g0uFypY8UDdr...

[eptcyka]

TLS1.3 breaks MITM boxes because a client can establish a session key outside of the network with the middle box and continue using it afterwards in the middlebox’s network.