I would not use rules to implement discontinuous changes in a SimBiology model. The ODE solver should be restarted whenever there are discontinuities, or else you may encounter problems like inaccurate results and slower simulations.
If you only needed to increase the value of a species, I would suggest using a SimBiology dose. But for more general kinds of step changes, I suggest using events. You can find one example of that here.
I don't know exactly what kind of pulse you want to generate. The plot I get when running the code you provide is different. But here's one way you could build a SimBiology model to reproduce what you plot. I use an event to toggle the concentration of a species between 0 and 1, and the event also determines when the next event will occur.
modelObj = sbiomodel("pulse");
compartmentObj = addcompartment(modelObj, "c");
addspecies(compartmentObj, "x", 0);
addparameter(modelObj, "nextPulseTime", 9.5, "Constant", false);
addparameter(modelObj, "stopPulse", 30.5);
addparameter(modelObj, "eventCount", 0, "Constant", false);
addparameter(modelObj, "numEvents", 22);
addevent(modelObj, "eventCount < numEvents && time >= nextPulseTime", ...
"nextPulseTime = nextPulseTime + 1", ...
"eventCount = eventCount + 1"]);
configset = getconfigset(modelObj);
configset.SolverOptions.MaxStep = 0.1;
configset.RuntimeOptions.StatesToLog = "x";
simdata = sbiosimulate(modelObj);
I hope that helps.