The "2nd shift" is probably just the converter locking.
After utilizing the tried and true, southern MD “pickup line” - “get in the truck, *****”, I took the wife out for a jaunt south in some traffic. A couple times in eco mode, the truck downshifted, thought better of it’s decision and went lower on the gear indicator. I haven’t noticed this in sport mode, but have in eco mode a few times and I will agree that 35-50, the truck is trying to get into the highest gear it can sustain. If I’m going up a hill, starting in 10th - I can only get 10th at about 50mph, the truck silently drops to 9th up a slight grade, will try to add boost to keep up if needed. but if I’m on level ground around 35-40 it’s up to maybe 8th, and adding just a little gas can initiate a shift that the truck seems to decide isn’t enough and digs a little deeper and produces better acceleration.
I kind of agree with Jeff-OH, if you compare the trans to a Town Car or Lexus, it’s unrefined in that you can feel a lot of the shifts, up and down. I rather like that, but I can see how it wouldn’t be brilliant in a luxe-barge. Eco-mode seems to be a little indecisive at times, a little busy at others.
Like it or not, automobiles exist in a caste system and the F150 and all it’s derivatives are in the “worker caste”. Take all the luxury away, and Ford builds the F150 to haul your a$$ and your $hit. The Lighting did that very quickly. Not for nothing, but the Raptor will quickly haul your a$$ and your $hit to places the busses don’t run, tow trucks don’t go and AT&T doesn’t have a cell signal. I know that last qualifier doesn’t narrow things down much but you get the point.
There are other vehicles out there with smooth shifts, less indecisive units, or less busy. Let’s remember that trans is delivering a --lot-- of power to the wheels of a 5500 pound truck.