I’m not sure how they got to that conclusion, but we can kinda guess.
The tongue is PACKED with blood vessels, so in case of any damage it can get tons of nutrients to fix itself. But this takes a very energy-intensive.
So if the rest of the body would have the same density of blood vessels, we’d need drastically more energy to feed all of that.
And I guess they’re asserting that all else being the same we wouldn’t be able to ingest or process sufficient food to keep that going.
It’s a bit of a strange argument though, I’m going far outside of my physiology understanding, but you’d have to imagine that had we evolved such advanced healing capabilities, we’d have also evolved the means to feed them. And OP underestimates just how much food someone can eat. As someone dealing with an ED, I can tell you that you can easily triple your calorie intake (though whether that’s sufficient I wouldn’t be able to say…).
All in I’d look forward to OP defending their assertion.
Remember these are people who know what it’s like to go through apartheid and ethnic cleansing.
South Africa today is largely governed by the people who fought and won against apartheid, so it’s understandable that they feel a level of solidarity with the people of Palestine.
(in this context I’m choosing to gloss over the real and present issues with the ANC, because they are not relevant to Israel’s genocide)