Hi OP here. Thanks for stating that. You are absolutely right. It isn't a technically correct analogy. I apologize for that. When I was writing the article I didn't want to get into the details for the non-injective surjection that is not reversal and that a function is merely relation where we shouldn't introduce the element of "time" by thinking of it as a process. I intended to go through the function section as quick as possible (the same time in a way that readers can easily form a mental image of it), and get started on differentiation and integration, which are what they are on my page for.