Here is a great example of why those fan style anemometers are so inaccurate. You claim 132 cfm at the hose connection. The motor in a CXL cannot produce that much airflow. Airflow in a vacuum motor is dependent on the size of the orifice. Vacuum motors make maximum airflow at a 2 inch or 50 mm opening. As you reduce the diameter of the orifice airflow is reduced. The OEM motor in a CXL is Ametek 116884-49. I have the Product Bulletin pdf open for that motor and will try to attach it but no guarantees it will load. Anyhoo, the maximum airflow at a wide open orifice for that motor is 115 cfm. That's it. The hose opening on a CXL is 28 mm or 1.1 inch measured with my caliper. Looking at the Ametek Product Bulletin at a 1.125 inch orifice that motor produces 90.7 cfm. That is all the motor can produce. It is physically impossible for the motor in that CXL to produce 132 cfm at the hose opening. In fact very few vacuum motors that are safe to use on a standard household 12 amp circuit make 132 cfm at an unrestricted orifice much less at the tiny 1.1 inch opening Tristar, Miracle Mate and Patriot use.
Here is how to think about how airflow is calculated by an anemometer. Think of a long tube filled with some fluid. The tube is moving at a certain velocity. The volume of fluid passing a point depends on the size of the tube, its velocity and the time period. The only thing any anemometer measures directly is the velocity. But lets say you want to know the volume of liquid that passes by the anemometer in a given time. Airflow is measured in units of volume multiplied by time, cubic feet ( volume ) per minute. Imagine your tube full of liquid flowing past your anemometer. The anemometer only knows how fast it is going. The tube could be 1/4 inch diameter or 2 inches diameter and the anemometer could not sense the difference. But for a given velocity the 2 inch diameter tube will pass a lot more volume past the anemometer in a given period of time than the 1/4 inch tube. That difference in diameter matters. But for anemometers that are used for commercial HVAC, most of the time the ducts are square or rectangular, so the meter I have requires the user to enter the surface area of the opening ( imagine a square tube filled with air rather than a round one flowing past the anemometer ) so the anemometer can accurately calculate airflow. Those propeller anemometers use the surface area of the round opening the propeller sits in, but that opening is a lot larger than the diameter of any vacuum hose so the readings it gives for vacuums are wildly inaccurate and almost always too high.
