I recall hearing it first another way, I think via Heinlein: "There is only one science. It is called 'physics.' Everything else is stamp-collecting." I like that phrasing better, because it highlights the disparity more plainly.
Anything that calls itself "science" must be based on observation, but only physics provides a predictive capacity from those observations. The other "sciences" consist only of collections of observations; those observations can be categorized, organized, and reorganized as new observations are collected, but they do not provide a predictive capacity. They do not tell you what your next observation will be with much certainty. If you find a strongly predictive capacity, chances are that there is a physics component underlying the observations.
Thus, the further you get from "physics", the further you get from "science."