Do dog raincoats actually keep dogs dry?

Reviewers across r/RunningWithDogs, r/BackpackingDogs and r/Pets generally say yes for the body, but with caveats. Shell-style coats (Ruffwear Sun Shower, Spark Paws) keep the back, shoulders and hips bone-dry; lower legs, belly and head typically still get wet unless the coat has integrated leg coverage like the Ellie zip-up. Verified-purchase reviewers note that double-coated breeds may not need one at all.