Porcaro was amazing. You can watch him play a groove unaccompanied and it still sounds great.That's the point exactly. I did some minor studio work many years ago, and I found the limitations of my technique quite a struggle. When you listen back it is not what you thought it would be because the mic picks up everything, the nuance or lack there of. Never mind the ability to do what you want to do. It's frustrating to be able to hear it but not be able to execute with the same ease and musicality that is going on in your head. Although I had studied a lot and had what I considered good technique, I didn't have the technical training necessary to really excel in the studio. It was a bad experience for me as a young drummer. Had I been more prepared, my story may have been a lot more positive.
Technique allows you to relax and that is a big part of it. I remember when I first played Home at Last with a band. There was those triplet figures on the bass drum. There was a certain place where I wanted those bass drum notes to land, and it was not easy getting that feel, getting them to land where I wanted them to land. It is splitting hairs because it is either in the pocket of it's not and the difference is minuscule. But when I got it to fit in, the pocket was so much deeper; it took it to a new level of expression.
You can talk about Rosanna as well, and the great feel; but the technique that it takes to drive the feel out of the groove is staggering, and Jeff Porcaro was one dude who certainly had it.
Studio work or just recording your playing with a band is a real eye opener for drummers.