The mini should be a perfect printing platform especially if it can run at least up to 10.13. (I had a 2006 mini for my scanner.) All this platform back and forth is so tedious since I can’t test anything Windows on my end.
A few years ago I made a series of ICCs using QTR-Create-ICC for several papers, and the results of each and every one of them were as in the graph I just posted. In fact, I soon realized that it wasn’t even necessary to make individual linearizations for each paper if I was going to make and use an ICC for each. I single “Master Linearization” was close enough for most papers that each ICC made from it was almost perfectly identical to the others. I thought of it as the great equalizer. Unfortunately, I didn’t really like the excessive darkening of the shadows. I did realize that I could custom shape the ICCs as well, but by that point I was deep into printing a project using a single paper and it just didn’t matter. I did use a tweak similar to the adjustment curve I posted above when making the final quad.
I have never seen a default ICC raise the highlight values at all so I have to wonder if you may have been unintentionally introducing some other influence, or maybe using it with a different quad that the one it was made from.