I changed the title to what a PR/commit title should look like.  Your justification is that "Multiple writes possibly cause excessive network usage and increased implementation complexity on the other end."

I see no problem with the formatting of your first post.

I presume the proposal is to make a list of bytes and then b''.join(the_list).  This is now a standard idiom.  Have you tested a patch locally?  Can you make a PR?

I don't know if there was a particular reason to not join before sending.  Perhaps because successive sends effectively do the same thing, though with the possible  downsides you note.  I am not an expert on network usage.

The _connect method was added by Senthil Kumaran in 2009 in #1424152 and revised since.  There is no current http maintainer, so I added as nosy  Senthil and others who have worked on the module.