I definitely think you are right. My best guess so far is that the only thing that would cause an issue is if I reused one of the ones that already exists. When I search through all event sheets/layouts sheets in the xml the SID variable never occurs more than one time; so, unique ID definitely follows.
That said, I DID find it in the data.js file. So my guess is, have to make sure that it remains unique in the event sheets and then when the project is exported these are used to reference the function/event. Is that what you found in your event sheet compiler?
In summary, it does have to be there and must be unique, but it can be arbitrary (seemingly) since the connection to the event is created on export.