Yes. I do not use the Brisk menu usually and noticed this today when testing things: with my Gtk theme (a Numix variant), the Brisk menu displays the GNOME (foot) logo and I still use the Ambiant-MATE icon theme. I switch back to the Ambiant-MATE Gtk theme and I got the MATE logo back on the Brisk menu.
I agree it’s weird, as it should use a logo from the selected icon theme without anything else mattering and indeed, after a quick check, the start-here-symbolic icon in Ambiant-MATE is the GNOME foot logo. So, it looks like it uses it. What is unexpected is that when using the combination of Ambiant-MATE Gtk+icon themes, it uses a different icon. Not sure why/how.
So, while replacing start-here-symbolic in the icon theme would likely work in most cases, I don’t think it’s the proper way to set it. Looking at the files installed by Brisk, there seems to be DBus stuff, so I wonder if it uses settings in Dconf/Gconf to choose the icon depending of the Gtk or the global theme used.
If you change it here I believe it changes Controls, Window Border and Icons, maybe even mouse pointer.
That’s absolutely right. The global theme files define the Gtk + icons + Metacity + cursor themes to use. In my case, I use a custom global theme that sets a Numix variant as Gtk + Metacity, Ambiant-MATE for the icons and the MATE cursor.