Earlier quoted context omitted.
Several knowledgeable vegans I know believe that they have real problems with oxalates in particular. This is particularly credible among people who drink a lot of spinach based smoothies, as I once did.
That's still very anecdotal.
Personally my long term dietary choices have been guided by N=1 experiments on myself, a.k.a. anecdotes, that have proven to be life saving for me. Anecdotes from others are useful for suggesting such experiments on myself, in the same way that epidemiological studies are useful for suggesting RCTs.