No you really can’t. Not when the tier pieces specifically say which slots give you the bonus and Blizz specifically says what slots give the bonus and a decade of tier gear establishes what slots gave the bonus. 
To finish the outfit and reforge stats. Why couldn’t you look at the tier pieces and read which ones gave the bonus?
The blue posts on this website ARE official source. And they specifically told you what slots create tier.
No one is making fun of you.
The screen specifically shows you what you’re getting. The loot table in game specifically shows you which pieces have set bonuses.
The wording was specific about which slots carry the set bonus.
Of course not. It just shows you the piece that matches the set with those specific stats on it. There’s no set bonus.