Indeed. delta U (and hence delta A/F) are measured under conditions of constant volume, e.g. in a bomb calorimeter. Most experiments are done at constant pressure instead; this involved delta H and hence delta G.
One last pedantic point, meursault. I think you mean "trigger" rather than "catalyst" in your last post. A catalyst speeds up a process that would occur any way, although possibly at a very slow rate; it doesn't cause something to happen that wouldn't happen without it. I doubt if we would have been discussing thermodynamics, even very slowly, without your original mention! (Sorry - this is one of my pet dislikes in misuses of scientific terms.)