Could the requirements for a heat pump be different? The backup heat is electric booster coils. No furnace.Either your figures are wrong, or your house was built without insulation or something crazy. 10 tons for a 2,300 sq ft house is completely insane. I'm in a 2,400 square foot house in MD and we have 3.5 tons AC, totally adequate. 80,000 BTU (~6.5 "tons") furnace which runs 95% of the time in the low stage of 52,000 BTU.
House is a well built in 2000. The two units were installed around 2015 or 2016.