The top-bar tag makes sense because it's specific.
Top bars, like in case of Budgie, Unity, or GNOME, are all used to do what exactly ? Have a few indicators, display time, connection, calendar, maybe have a menu/list of all programs. And it stays....well...on top and usually areis an integral part of the desktop environment.
Then there's docks, bars, panels, launchers. There's mate-panel
, lxpanel
, lxqt-panel
, xfce4-panel-dbg
, razorqt-panel
. While those can have applets for calendar, connection, time, etc - they're (re)movable
and separately-installable! I can have Budgie running and still have mate-panel
on top. But then there's docks: docky
, plank
, cairo-dock
, tint2
(which calls itself panel/taskbar
) etc. They're also (re)movable and separate from desktop. While they can be placed on top of the screen, they're not necessarily meant to be there.
I think synonimizing the two only adds confusion, especially in the comments. Imagine the conversations:"Are you talking about the GNOME 2 panel or that side launcher ?". Whereas when I see top-bar that'd be a clear indicator (all pun intended) what the user is talking about. But then again, this is just my very much biased opinion.