I don't believe that this is a valid argument. I doubt if Microsoft has cribbed the Arduino implementation of the String class to use in its library functions.
Then you haven't read the article. It is referring to the underlying dynamic memory, which is used by the String class. Belief and doubt have no place in rational discussion. Unless....
I see this all as a religious argument
Oh. I thought this was a factual discussion, with supporting material from a variety of sources.
the same arguments apply to anything which makes the run time unpredictable which would rule out recursion, automatic variables, the new operator etc.
Then you really don't understand determinism. Recursion, auto variables and the new operator can all be used in a deterministic way. Random-sized heap allocation and unlimited growth is not deterministic.
until... replaced with a younger generation who want nothing more complicated than dragging and dropping icons to create code.
Then why complain when we offer something more complicated, yet more stable and efficient? Fight the future!