I agree that there was likely a bad expirience that resulted in that recommendation. I have hear of transmissions not being serviced for a really long time resulting in the friction material breaking/wearing away and into the fluid. Instead of the clutch friction disks holding, it's the friction material in the oil.
You flush the oil, and now the friction material is now gone.
How I look at this, is if the oil is changed and the transmission starts acting funny, there was a problem before the flush and it's not a problem with the dealership or the work if the work was done correctly. However, the customer may not understand or want to understand this.
On the flip side, any time I go into a dealership and listen to them try to upsell maintenance or snake oil to unknowing customers it reves my engine.
Now I do believe that some services can improve a vehicles drivability such as a fuel injector flush, but if you use good fuel there are detergents in the fuel to prevent build up.
Transmission flush chemicals I never understood because transmission oil in naturally highly cleansing. You can use old fluid to clean parts or use it to cut with engine oil to clean out the engine. (That last part is not endorsed by Ford, just and old school procedure)
Aftermarket Coolant flushes are a wash, I dont know what they are made up of or what they do. Ford has chemicals for specific vehicles and procedures for the flush including our cars.
Brake fluid flushes are a good idea every three years or so. BUT no cleaners are really needed. Just pour in new fluid and use it to push out the old. (I do recommend pressure or vacuum bleeding. Reason being is if there is debris in the master, your not going to run your seals through them during this kind of flush vs pumping the brake pedal through it's full stroke)
We don't have power steering fluid, but changing this is a good idea if you have a hydraulic system. No chemicals are really needed, just drain and fill a few times. Most of the time its ATF so again, a highly cleansing fluid. Changing the oil can also lessen that whine noise on cold starts from my expirience.
Fuel additives for water, or ethanol is a waste to me. The ethanol in the fuel is going to absorb the water in the tank if there is any. You can by something aftermarket if you want, but ford does sell a cleaner to add to your tank if you want an approved chemical. Funny enough, I couldn't find a local dealership that sold it.
Any how, if you have read to this point, you have a few options about your disappointing visit. Call and leave a message about the particular Service Writer to the service manager, or you can call the Ford Customer Relationship Center (CRC) at 1-800-392-3673.
I have also added an attachment that is available to all dealerships about maint. Flushes and aftermarket chemicals.