Your suggesting parents in the past watched their kids starve to death?
50 + years ago my DGP tolerated my parents food issues as much as they could - because they were loving parents.
There's many a parent with a child admitted to hospital on MN because their kids have such extreme food issues they don't just eat.
ND/SEN have always existed - but sociteies were with more tolerant or the kids died young. There a huge gentic component - and many with these conditions in past have managed to be successful they were just veiwed as odd or if rich enough eccentric.
Now I do think you can put in support and find ways for the kids to manage as best they can - that's the approach I've taken with my kids - but more extreme the issues less that's going to work.
I don't know how the Tennat parent - probaby as they are arty middle class Londoners very differently to how I raised my kids but no-one can just discipline the ND out a kid - and while maybe a differnet dinner table appaoch might have worked many times parents have tried and found their ND/SEN kids need different methods to NT kids.