Snare Drum Factory Creates Harmony

That looks like the default Preview progression. So I suspect there is simply no SD generated at all (due to odd probability settings). In which case Synfire shows the next best available parameter.

The same Line Factory is also used for multi-line phrases where it is legitimate to have individual lines that are empty if some probabilities are low (e.g. a bar that happens to go w/o a snare but with other instruments).

If a factory is used standalone as an isolated line, you suggestion makes perfect sense.