Who is unreal "designed" for?

[Absurdity]

Because they're attempting to showcase what these old EXs were like during their respective peak. Without an ilvl sync, we would utterly obliterate them.

I can somewhat understand the reason for trying to keep them relevant but it's not like this wasn't the case back in ARR. Just like most extreme fights are outgeared today as soon as they release or soon after, their old extreme fights were the same.
They could've just as easily released them at 10 or 15 ilvls below the current max, like a normal extreme and kept them relevant without making it a frustrating experience for most "midcore" partyfinder groups.