Special handling of Expect: 100-Continue may not be appropriate in a proxy

I'm using Akka HTTP (3.0.0-RC1) to create a reverse-http-proxy. The special handling of Expect: 100-Continue looks like it's causing weirdness in this case. In wireshark, here's what I see:

Proxy  -> RSP: 100 Continue -> Client
Client -> REQ -> Proxy
Server -> RSP: 100 Continue -> Proxy
Proxy  -> REQ -> Server
Server -> 200 -> Proxy
Proxy  -> 200 -> Client

In the production logs (not in an attempt at a clean room reproduction) we see a number of these messages:

Sending an 2xx 'early' response before end of request was received...

It's not 100% clear that these are related to the special handling of 100, but they do seem to coincide a lot. It feels like the special handling should be avoided when akka-http is operating as a proxy, leaving the handling logic up to the server to which we're proxying.