[StanStr]

Brake fluid cannot be changed from the "top."

You can't really 'change' it without flushing it. Which means replacing all the fluid in the brake system (master cylinder reservoir, the lines, calipers...). Some say it's not necessary, that it should be done maybe half as often as Honda says, if ever. You really should bleed them about as often as the book says.

Brakes operate under pressure. They get really hot, the fluid breaks down after a while, they get mushy and your stopping distance increases more than it seems. You didn't expect the guy in front of you to stop. You jam on the brakes, and give a sigh of relief that you just tapped him. You both get out and you just dinged his bumper. You exchange insurance info. You give another a sigh of relief. A week later you get a call from insurance asking about the accident... That the guy you hit and his wife's mother both have whiplash injuries - and their car is at the dealer for accident repairs.

If you want to see if they really changed your brake fluid / flushed the lines, take a look at the master cylinder. Did someone wipe the grime off the cap so they could open it? Open it to see if the fluid in there is clean. Don't mess with the fluid itself, it eats paint faster than you can wipe if off.

Now, excuse my rant...
The best way to make sure it, and anything else is done really properly is to avoid the dealer. Find a good reputable local independent mechanic. Anything an independent does will cost a lot less. You won't have to talk to a service writer, but to the mechanic. When I bought our Odyssey and the CRV I only took it to the dealer for warranty work and recalls. (It's nice. they have a fancy lounge and coffee, doughnuts, fancy cookies, WiFi and more. They also wash the car, vacuum & wipe down the interior, and clean the windows inside and out. They get me an Uber to work and pick me up later. Just for a seat belt fix or air bag recall.)

The independent shop I go to is in an industrial area in a place with other auto related shops, and a couple other somethings. It isn't fancy and clean as the dealer. BUT the guy wrenching knows his stuff.