Downhill braking causing engine to rev

I had this happen to me a couple times, and if this is normal, kind of disconcerting. I am glad I checked here, the dealer wanted to charge me a diag fee, even with the truck only having 35k on it. Is there anyway to not have this kick in? I was going down a hil around 50 mpg, and iit did this, and my brother made a comment about it. I have had this happen one other time. And, yes, the speed limit on those roads were 55 and 35, respectively, and I was going the speed limit,

 

If you want it to kick out just tap the gas . I like the feature and use it .

 

I dont know that I ever noticed this. As habit I always kick it to S mode on long or steep grades. Hot brakes suck.

 

Netural...?

 

I use it all the time tap the brakes on a steep long hill to let the truck downshift, and tap the go petal to get out of it. Often wished my old tundra did this.