I don't think this article is very well-written. It gets confused about whether QUIC has a handshake or not (it does). And it conflates zero round-trip time with combining the TCP/TLS handshakes together.
I came to mention the same. Diagrams have redundant information, examples are badly picked, there's sentences with little to no value... I don't know if it's lack of care, the author not writing in his native language, or excess of GPT.
> QUIC works on top of UDP. It overcomes the limitations of TCP by using UDP. It’s just a layer or wrapper on top of UDP.
The article says this repeatedly, but it's also wrong about that. QUIC doesn't use exactly the same three-way handshake at the beginning of the session -- but it uses a handshake that lasts at least 3 packets.
> QUIC works on top of UDP. It overcomes the limitations of TCP by using UDP. It’s just a layer or wrapper on top of UDP.
Makes me want to stop reading.