I cannot imagine any student
pilot being capable of flying an approach in actual conditions, nor
an
instructor allowing a pre-PPL to do so.

You lack imagination. I've allowed a student pilot to fly an approach
in IMC, and he actually did quite well for a while (with a lot of
coaching, obviously). This was a much more demanding approach (night
circling NDB) in a much more demanding airplane (my Twin Comanche).
Eventually he started losing it (meaning he could no longer keep up
with what had to be done even with my coaching) and I had to take it
from him and complete the approach myself.

There's nothing wrong with an instructor allowing a student to fly an
approach in actual IMC - as long as the instructor is prepared to take
the airplane before a dangeerous situation develops.

There's no question here that the approach was mishandled, and I don't
consider it important to know who was actually manipulating the
controls. In any case, the CFI was PIC, and he was responsible for the
control inputs of the student. I suspect he simply got overloaded
trying to teach in IMC (or perhaps just fly in IMC). Either way, it
hardly matters. He overestimated his abilities, and has now paid the
ultimate price. His student paid too, and his only mistake was
overestimating the capabilities of his instructor. Sad but hardly
unique.

Michael