I'm having the same issue but I have yet to see it explained anywhere.
The only difference in my code is that in the .phtml I use "form" instead of "login" as suggested by the tutorials.
PHP Code:
<?= $this->form->submit ?>
However when I run this code I get errors because "form" is not an object. I have dumped the contents of "$this" to the screen from the custom view script and I can see all of the correct data and elements but I do not see the correct way to reference them. Has anyone successfully corrected this error?