New HVAC system --2 stage a/c; variable speed heat/fan

I'd not complain to him, but there is no harm in asking for an explanation of how it is working. Technically, if it changes from high to low it is a variance.

You must have a huge house in the desert to need 5 tons.

I'm sorry, my crystal ball is unable to connect to your HVAC system.  Please supply us with the make (both Ruud) and model numbers from your indoor and outdoor units.

Unless the thermostat is some super smart one that's made by the furnace manufacturer and required, it's not going to know what speed the fan is running or have any way of indicating it. And that's the kind of thermostat you want, a smart, easy programmable one that works with any system, not some proprietary expensive one that you can only get from the manufacturer. I recommend the Honeywell VisionPro series.

These furnaces have settings that control things like max blower speed, which speeds it uses for heat and cooling, etc that are set with dip switches on the control board inside the furnace. First, I'd find the exact model of the furnace. That may require pulling the door from the burner section or the blower. On mine I think it's in the burner section, on a label. With the complete model number you should be able to Google and find the specs which will tell you what kind of blower it has. Possibilities include:

two speed regular motor two or more speed ECM motor that is more energy efficient variable speed

And with the model number, Google for the installation manual. That will show the switch settings for all the options. They are not always available, but Ruud/Rheem is sold by some of the online houses that will sell gear to anyone and they may have it.