I think you may be a bit harsh on
@gizmo as we are talking about "purity". How pure is pure enough?
I'm a purist, also a frugalist (is that a word?), and have spent many months on "natural" safaris.
Let me set the stage with two anecdotes:
1.) I contracted to have access to a wilderness safari area that was a 10-mile radius. It's a pretty sizable area. Was it clean and pure? Well, no fences, for sure. No houses, for sure. No stocking, for sure. It was certainly a huge wild game migration corridor. That's 314 square miles. That's 1/4th the size of Rhode Island and it was wild and all for me. Deep in the bush on a stalk, I found the sole of a Nike tennis shoe. (modern) Of course, I also found dozens upon dozens of spent rifle cartridges, most of them kynoch or Martini-Henry from the 1880s - 1930s sitting on rocky ground exactly where they were ejected a century or more ago.
2.) In another wilderness area some 500 miles away from the former, 20 miles from camp, deep in the bush, 40 miles from the closest village, on the spoor of elephant, I found a US Food Aid corn-meal sack.
Bottom line, purity is a matter of degree rather than a matter of Yes/No. This applies to fences, wildlife fair chase, natural breeding, natural migrations, and human encroachment.
I assume based upon Zimbabwe as an example (I've been to all but one of the Zimbabwean provinces/districts) that the rest of Africa is similar. No matter where you are, man has been there and left a mark. That mark has altered the landscape in some manner.
All of that being said, I do feel that there is a great desire to extol the virtues of fenced operations for one biased reason. That is the type of operation most operators can provide. They cannot provide a no-fence or wild operation. Whether via poaching, customer accommodation demands, security, protection of property, or economics, fences are what must occur. Knowing that is what the operator has to sell, of course they are going to attempt to convince the customer that its just as good or better than the product the operator cannot provide.