The current draft states both
A client which receives a TLS 1.3 Server Hello with a legacy_version value not equal to 0x0303 MUST abort the handshake with an "illegal_parameter" alert.
and
Any endpoint receiving a Hello message with ClientHello.legacy_version or ServerHello.legacy_version set to 0x0300 MUST abort the handshake with a "protocol_version" alert.
Which would seem to require sending two different alerts if 0x0300 is sent in a ServerHello.legacy_version. This seems unlikely to be intentional. If it is intentional it probably deserves more text. If it's not intentional the alerts should be the same for both cases. Given that RFC 8446 already required protocol_version be sent (for the second requirement) I'd suggest the first requirement (which does not appear in 8446) be modified to also require sending protocol_version.
The current draft states both
and
Which would seem to require sending two different alerts if 0x0300 is sent in a
ServerHello.legacy_version. This seems unlikely to be intentional. If it is intentional it probably deserves more text. If it's not intentional the alerts should be the same for both cases. Given that RFC 8446 already requiredprotocol_versionbe sent (for the second requirement) I'd suggest the first requirement (which does not appear in 8446) be modified to also require sendingprotocol_version.