This seems like another example of protocol ossification[1] (servers making assumptions about a protocol based on how it's used in practice, which breaks things when how it's used changes), in this case due to servers assuming the client hello is below a certain size.
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[ 0.30 ms ] story [ 19.1 ms ] thread[1] https://en.wikipedia.org/wiki/Protocol_ossification, https://blog.cloudflare.com/why-tls-1-3-isnt-in-browsers-yet