Quite possibly. Service dogs don’t have to be large, or the center of attention. Sometimes they ride quietly in a pet carrier, without being noticed by most people. They allow their owners to go about their lives without the whole focus of their lives being about the dog, and educating the public. Sometimes disabled people just want to run errands, like anyone else, without having to explain themselves two or three times at every stop.
Sometimes scammers just want to run errands, like anyone else, without having to explain themselves two or three times at every stop.
And, there's the rub.
But, you are right. There is no reliable way for anyone to know if someone really needs these animals under their table in a restaurant or not.