"close other tabs" on app tab context menu should be disabled, not hidden for a similar discussion see https://bugzilla.mozilla.org/show_bug.cgi?id=594176#c6

See bug 577121 comment #10 for original decision

I'll let alex make the "yes please"/WONTFIX call, but it doesn't block, regardless.

App tabs are going to ultimately have different context menu commands than the tabs in the normal tab strip. Currently this is one of the only differences (which is why disabled seems to make more sense), but going forward we for instance aren't going to want to have app tab specific commands disabled for normal tabs and active for app tabs. So even though it momentarily looks like a mistake, the overall goal is to create two sufficiently different context menus for app tabs versus normal tabs.

so what about "move to group"? should that be hidden now?

yeah since app tabs are global that should be hidden as well.

filed Bug 609495 per comment 5