I'm no expert, but origin wise, I assume that you are right, olives and legumes were grown the levant for thousands of years, so balila is a very old dish.
One can assume that msabaha was invented with the import of seaseme. And I guess that hummus originated from msabaha by pounding it smooth.
Now days, msabaha is not simply hummus with whole chickpeas. Hummus in Israel is almost always served with whole chickpeas (unless topped with something else). Msabaha has many versions, but all are served warm, are usually more fluid, contains more tahini and may include a small amount of chili (chili is never added to hummus).
My version starts with chickpeas cooked very soft, I make tahini sauce with lemon and spices (garlic, chilli, cumin), then mix a portion of the peas using a fork until they break and thicken. Then add the rest of the peas and mix gently. I also mix in parsley, which is usually only added on top.
