Haven’t done any squeeky toys myself, but for the dog toys I’m thinking of, I would have assumed blow molding since usually there is a good smooth finish and an obvious clamp mark for a gas injection point, plus the smaller size and surface finish.
For anything I’ve seen rotomolded I always felt like it was larger parts, poor exterior surface quality, and usually the higher cycle time makes it not great for super cheap stuff.
But I admit I could be wrong and just basing those assumption on samples I saw long ago. Never touched either process in my line of work.