On your link page:
5 chrome/browser/flag-metadata.json
@@ -3179,11 +3179,6 @@
"owners": [ "//device/vr/OWNERS", "xr-dev@chromium.org" ],
"expiry_milestone": 76
},
{
"name": "windows10-custom-titlebar",
// "owners": [ "your-team" ],
"expiry_milestone": 76
As all the flags are purely experimental, they are subject to being removed at any time. They allow functionality for a time and then remove it later. Removing the /flag is easy but removing all the function code takes time.