I am so confused by reading this. lol
I am playing wow for 10 years now and I have no idea what you all are talking about. I feel left out

reached 1445 2v2 rating back in 2014 and have a couple of mythics under the belt but as far as macro's go /challenge /lol is as far as it goes for me. think I can up my game a bit more to understand what you'all talking about here!
tl;dr:
It doesn't matter unless you play low level pve.
Long version:
In Warlords of Draenor blizzard did something called a "stat squish" which lowered the stats on every item in the game in order to bring damage/healing/health numbers to a more reasonable level. That also meant they smoothed out the power curve from 1 to 100 (meaning you gained less stats per level than you did before, relatively).
Because of the stat squish, there was no longer a big stat difference between low and high tier gear within the expansions. For example Karazhan gear was now comparable to Sunwell gear stat-wise, whereas previously Sunwell gear would've been a lot more powerful.
So in order to "fix" this lack of a power gap between tiers, blizzard stealth implemented a system we started to call "the item level boost", which made your character more powerful while within PvE instances based on their item level. Kind of like the PVP stat template system that came out one expansion later, but different, because this one didn't change your stats, it just made you do more damage, more healing and take less damage in the form of flat percentage modifiers.
The end result was that Sunwell gear was still generally the best gear to wear (not because of its stats but because of its higher item level).
Fast forward to the Battle for Azeroth pre-patch when they implemented
another stat squish, this time including an item level squish as well. After the pre-patch went live we were quickly able to confirm that the item level boost system was still active in low level PVE instances, but because all the item level values had changed we were unsure of the exact numbers.
That's what this thread is about; Shinela posted a macro that allows us to check exactly what damage/healing/reduction bonuses we are getting from our item level again.