That's what it sounds like to me as well. I have to admit though, I've never really given 225.21 and using UF cable much thought together, since normally the only cables I attach to outside of buildings are usually SE/SER, coax and/or telephone, but it's good to know anyway, should the need ever arise.
This also gets me wondering if standard steel #12 or #15 staples like we use for NM cables in dry locations are actually listed or otherwise designed for use outside to secure UF cables to buildings. I've seen them used for this, but they always seem to be rusting quite badly.
I know that my local supply house now carries stainless steel #15 staples, which I assume would be designed for indoor/outdoor use, but not sure about this.