Right on their website. Go have a quick look. Trust me I went to Kawasakis page and saw the fr motors being advertised as residential so I am skeptical as you are!
Can't find anything on the Toro website(can you go to the webpage you saw that on and copy & paste the link here), but they may be regurgitating what I read on the kawpower.com website. On the "engine webpage" they "describe" the FR, FS & FX series as below:
FR - Commercial-grade power for heavy-duty residential use.
FS - Specifically engineered for demanding landscape work.
FX - Top of the line power and reliability for high-demand use.
Now if you click on the FR series it says: "For decades, professionals have known the value of having a Kawasaki engine in their equipment. Now homeowners can enjoy the same Kawasaki power in their mowers. Introducing the all-new FR Series engines featuring four-cycle V-twin powerplants which range in size from 18hp to 26hp. They deliver smooth power output, quieter operation, outstanding durability and compact design."
For the FS it says: "Kawasaki FS Series engines are engineered to be high powered but still environmentally friendly. They feature a compact, 90ー V-twin design with overhead V-valve, as well as an internally vented carburetor with a fuel shut-off solenoid. There is also a dual element air filter with a plastic blower housing that makes for quieter operation."
For the FX it says: "Kawasaki FX Series are compact, 90-degree V-twin engines which feature hemispherical combustion chambers and overhead V-valve technology that helps ensure low emissions, high power, and smooth operation. Other features include a twin barrel, internally vented carburetor with fuel shut-off solenoid, large capacity fuel pump, and dual stage canister air filter."
Soooooooo, based upon the verbiage used on the Kawasaki website you indeed could advertise the FR series as "commercial-grade" engines. Yet the details clearly state that the FR series was designed for homeowner use. It's all about how you interpret the information. To me(my personal opinion), I consider the FR series an appropriate engine for homeowners who mow 1-2 acres or less weekly, the FS series an appropriate engine for homeowners with 2-4 acres who mow weekly or a small lawn maintenance business that may average 2-4 hours of mowing daily and the FX series for the large lawn maintenance business that mows 8 or more hours daily. At least that's how I would choose if I fell into those owner categories. Of course that's not completely realistic since many, like myself, do not mow like a large lawn maintenance company(I am a homeowner who mows 1.5 acres weekly)....yet I bought a ZTR with a Kawasaki FX engine:0)