Perhaps we should make a L3 heading, "Can you use your element with a screen reader?", and make this and the below heading L4 headings.

We could then include some intro text about screen readers in between the L3 and L4 headings, perhaps:
"""
Around 1-2% of users will be using a screen reader[1]. At the end of this document, we list some screen readers which are free to use: try using your element with at least one of these screen readers. Can you determine all important information and interact with the element using the screen reader and keyboard alone?

The following questions should help guide you in addressing screen reader accessibility:

...

[1] Due to privacy concerns, it's difficult to get accurate statistics on screen reader usage, but surveys suggest that this is a realistic figure. If 1% sounds like a small number, consider that large companies often run UI experiments on 1% of their audience and use this data to drive design changes. (May not need this note at all, just a thought)