Wyttenbach: I suggest you distinguish, as I do, between endothermic reaction and phase change?
Never ask a chemist that he has to run a reaction just with fluids. Very often powders are used, which much be dissolved = melted.
On the other side a huge part of the reactions are fluid-fluid and end up with a solid, which frees the crystallization energy. That's chemistry not step by step physics. The energy of all steps must be properly calculated in.
From a pure physical logic You are right. But don't expect that only people with at least a bachelor in physics read such post's or that physicians decide how to run chemical reactions. The melting/ dissolving is a part of the reaction.
Thus don't talk about fields You are not educated in.