'16 Mustang, V6, 6 speed auto transmission, 63,000 miles on the clock. I bought in new in '16, so one owner.

It's a meticulously maintained car: full synthetic oil changes regularly, don't "drive it like I stole it" so no burnouts, daily driver/grocery getter, & I put on about 200 miles a week of Interstate driving & VERY little city driving.  The constant "Italian Tune-up", if you will.

Question is this:  Over this past weekend, I took her in for an oil change (I have all maintenance done at the dealership where I bought the Mustang) & inquired with the service advisor about the transmission fluid change.  I told him that IF...I wanted one, that I did NOT want it flushed out, but only a fluid change.  He tells me that if they only drop the pan to change fluid, that only a small amount of fluid will be changed & a system flush will make sure to get ALL fluid out.  This is where the hesitation comes into play, hence my question to the REAL experts here.

I've seen enough of Scotty's videos over the years (& being an "old school" car guy myself) about flushing out the fluid in an auto transmission to be very leary of a power flush.  It shifts perfectly, & drives like a dream on the Interstate so I don't want to ruin a good thing!

Is the service advisor only trying to sell a service just for the $$$ because only dropping the pan & changing the fluid is far more inexpensive, or is this a genuine requirement on this year's transmission?

Thanks, people!