I have this same question and can’t find a clear answer. Some say absolutely not, some say expansion joint, some say waterproofing, some say saw it out and run concrete under the stucco. we would like to walk out of our house without a large step down to a patio, Right now our door sill is about 16” above grade, and we want to pour concrete just 2” lower than the door so it is wheel chair friendly. This would cover 8-10 inches of our stucco wall, 6” of which would be above the foundation. Back fill & Concrete to stucco to foam to sheathing to framing. Phoenix, Az. I see all sorts of issues… my husband says it’s fine, don’t worry… what say you?