It is actually pretty simple. Let's set this aside first. To me, an animal behind a fence, whether in Africa or Texas, is not the same as a free range animal. That is not meant as a blanket condemnation of game ranch hunting - I have done it and written about it. But, I think my assertion is largely correct.
The US, like parts of New Zealand and Australia, is host to a number of nonindigenous species that have flourished here in some cases for more than a century, and represent wonderful free range hunting opportunities. These are truly wild animals existing naturally in a free range environment. The aoudad, scimitar horned ibex, and nilgai have proven particularly successful introductions in Texas. For all practical purposes, those animals, are now native.
In that native environment, they are exceptional game animals.
Under most Hill Country game ranch conditions, nilgai and aoudad especially, are something to shoot as they stand around a feeder. That is also true of of our 230" Frankendeer that are priced by the inch.
So let's turn to Africa. A lechwe behind a fence in the Eastern Cape is no more native than an elk behind a fence in the Hill Country. Neither hold the least interest to me. Should someone else wish to shoot either under those conditions, that is absolutely fine. Just don't expect me to be mesmerized by the tale of the hunt.
But a Lechwe, from the Caprivi or the Kafue is a remarkable quarry with a story to tell about its environment. Were there a created and established free range population along the Limpopo, I think one could say the same about it as one would an Aoudad in near Marathon, TX. I am unaware of such a population.
Finally, these are purely my personal observations and conclusions. I in no way believe they are necessarily superior to someone who feels very differently about a Lechwe or Hill Country elk. But, they are right for me.