Do you know if they ever got around to fixing this?

The fix using frame modifier doesn't work for me...

The "fix" of using a frame did not work for me. Really annoying problem!

One option to create a virtual machine using VirtualBox, VMware ESXi, etc., running some prior version of macOS. There are lots of guides online regarding how to do this. If you don't want to waste disk space on your primary dev machine with ancient Xcodes, It's also easy and cheap to just get a used Mac for running older software. The 2010 Mac Pro towers are pretty cheap these days.