It's not entirely WolfSSL's fault. TLS 1.3 is a mass of kludges and hacks to deal with the fact that they created a new protocol that's nothing like TLS 1.0-1.2 but dressed it up to make it look like TLS 1.2. It even lies about its protocol version in the handshake, hiding the real version in one of the many extensions they had to invent to kludge it into working. And in terms of RFC compliance, one of the most widely-used implementations isn't compliant, it doesn't send any of the mandatory-to-implement cipher suites in its client hello which means unless you want to trigger a rehandshake on every single connect you have to implement their non-compliant form of TLS 1.3.

The real problem though is that they made a protocol that really, really wants to pretend it's TLS 1.2 when it really isn't anything like TLS 1.2. I wouldn't blame "middleboxes" for getting confused when they encounter that.