It's simple, load the USB loader GX forwarder and select homebrews and load them from there for now, it will load ALL homebrew apps in 16:9, and so far I cannot load homebrew channel from there. but it's a good workaround for now.
UPDATE: and bump. using the homebrews loader on USB loader GX, select the title loader on the bottom of the screen and load ANY wii channel in 16:9, including the HBC. this includes ALL virtual console games.
The problem is because HBC's current title ID begins with an L I believe, which is the letter of some VC games and Nintendo changed the code to make those VC games display properly. Any channel beginning with a letter that isn't used for VC games should work fine. HBC will get an update to fix it, but there's some other stuff that needs done too.
Now that tueidj has posted his fix, I'm interested in booting certain games with the 4:3 aspect ratio format, as it is the only way I've found for keeping the proper aspect ratio when playing GCN games using Devolution on the Wii U GamePad.