Here’s one other solution I tried, but it did not work, it just spits out <p><!--nextpage--></p>:
<?php while(has_sub_field("content")): ?>
<?php if(get_row_layout() == "section_content"): ?>
<h2><?php the_sub_field("section_title"); ?></h2>
<?php
$section_text = the_sub_field("section_text");
$section_content = $section_text . '<!--nextpage-->';
$content = apply_filters('acf_the_content', $section_content);
echo $content;
?>
<?php endif; ?>
<?php endwhile; ?>
