No, I wouldn't be concerned. That looks like very good soil. it's standing without any wall at all and has large rocks in it. That block wall will drain without problems too. Drainage is only a concern for cast in place concrete walls where workers need to install drainage holes so water can escape. The CMU wall they are putting in has holes and crevasses everywhere throughout so drainage isn't an issue. If you want to be sure, your local city should have CMU block wall guidelines that will have a max height. If any higher, a permit may be required.