ProxyProtocol in nginx documentation correct?

[curatorsigma]

I have just put a stalwart installation behind an nginx (1.25.3) reverse proxy via proxy_protocol for IMAPS, but I needed to use this config snippet:

server {
        listen 993;
        proxy_pass 127.0.0.1:10993;
        proxy_protocol on;
}

The documentation has

    server {
        listen 993 proxy_protocol;
        proxy_pass 127.0.0.1:10993;
        proxy_protocol on;
    }

This asks the proxy to expect proxy_protocol connections from the client. The client does not speak proxy_protocol, so this breaks (nginx error: broken header: "xxxxx" while reading PROXY protocol). We want nginx to "upgrade" a plain TCP stream to proxy protocol.

Is this a typo, or have I misread the docs or am I missing something else about nginx config syntax here?
Nginx docs:
accepting proxy protocol
proxying via proxy protocol