They might be running a scam on you. (A dealership scamming someone, how could that possibly be??)  However there are seals where the axles connect to the transmission that can wear out and go bad. It's even possible the dealer messed up one of the seals while working on it.

I'd fill it to the proper level and keep an eye on it, maybe put a piece of white posterboard underneath to see if any trans fluid is dripping. Now if you have a leak you can confront the stealership but I suspect you won't get anywhere on an 8-year old vehicle, they'll claim it's "normal wear", "not their fault". If that's the case and you need to get it repaired take the car to a good independent mechanic (not a chain like Pep Boys, Midas, etc.).

I assume your Fit is front wheel drive? They don't have a dedicated "drive shaft" like a front engine, rear wheel drive vehicle such as a pickup truck does. They have what's called a transaxle, which is a complicated combination of a transmission and differential. That connects to drive axles, which connect to the wheels to transfer power to them. Sometimes, pulling those axles out of a transaxle can cause it to lose some fluid, which should have been replaced by the dealer technician when they replaced them. Pulling the drive shaft out of a classic rear wheel drive vehicle can cause it to lose some transmission fluid through the tail shaft. When truck guys replace them, they're supposed to have a drip pan ready to catch it, like draining motor oil. Keep an eye on your fluid level, and if something is now leaking after they touched it, I would be making them fix it on their dime, or tell Honda what's happened. 

If the seals on your driveshaft are loose, you may loose ATF. Take the car back to the dealer and have them fix it. 

Your "dealer" is clearly scamming you.  Find an honest, independent mechanic.