Implementation details - even just partial sketches - are always
"busy".  Think of it this way instead:  it's _currently_ the case that
listcomps & genexps run in a scope S that's the same as the scope C
that contains them, _except_ that names appearing as `for` targets are
local to S.  All other names in S resolve to exactly the same scopes
they resolved to in C (local in C, global in C, nonlocal in C -
doesn't matter).

What changes now?  Nothing in that high-level description, except that
a name appearing as a binding expression target in S that's otherwise
unknown in C establishes that the name is local to C.  That's nothing
essentially new, though - bindings _always_ establish scopes for
otherwise-unknown names in Python.

That's a very nice (and short) explanation!

Maybe my distrust is just don't like the new syntax, or that I'am biased towards using "as".

--
Juancarlo Añez