EOS 3.1 supports UDP packets which is fine for data that prioritizes speed over reliability. That works fine for data that will reliability resend again. However, for single "cue fire" type "one time events" it is more important that data reliability (TCP) is used, and some third party applications only receive TCP packets for this reason. The OSC spec says both are options, but does not require both. Clearly ETC sees the value as it will receive on TCP or UDP, but it appears to only send over UDP.