ProxyRemote with https remote-server sends GET instead of CONNECT

My Apache httpd proxy server has an upstream proxy that only accepts HTTP CONNECT method.

According to https://httpd.apache.org/docs/2.4/mod/mod_proxy.html#proxyremote

When using https, the requests are forwarded through the remote proxy using the HTTP CONNECT method.

I added the following directive to httpd.conf:

ProxyRemote "*" "https://127.0.0.1:9051"

However, when a client sends a proxy GET request it's not converted to a CONNECT request, but is passed through unchanged.

Did I misunderstand the doc? How to make Apache convert the first proxy request to a site to a CONNECT request to the upstream proxy? Here's the desired conversation with HTTP keepalive:

browser                          Apache                 Upstream
   >> GET http://site-a.com/page1
                                >> CONNECT site-a.com:80
                                       >> GET /page1
   >> GET http://site-b.com/page1
                                >> CONNECT site-b.com:80
                                       >> GET /page1
   >> GET http://site-a.com/page2
                                (reuse existing site-a connection)
                                       >> GET /page2
   >> GET http://site-b.com/page2
                                (reuse existing site-b connection)
                                       >> GET /page2