The Bluecoat sales people did a number on you huh? Sounds really good until you ask 'why doesn't Bluecoat understand this traffic' - because it really should.
>>icebra+Ob
This is a failure to implement any version of TLS correctly, not just v1.3. (TLS has support for version negotiation including receiving a hello from a client with a future version, such as v1.3.)