Yes, I just checked it. I used a socks proxy to my VPS thru putty, downloaded version 1.8.1 pre-3 thru it . I attempted to join a server.and the server log join message showed my connection as coming from my home IP address, not from the VPS proxy. So yes this bug still affects 1.8.1 pre-3 If anyone wants specific logs, let me know.
Using a socks proxy for the game traffic as well as the launcher is no less secure than playing minecraft via a VPN, and as far as the account system itself is concerned is no less secure then making a direct connection.
Without the security argument the only reason for not making a fix for this bug is that they are just too busy to be bothered with such trivial things, not realizing the living hell they are making some people's lives that are required to use a proxy for their traffic.
Failing that its just sheer laziness I guess :/