In Section 4.2 "Text Alternative Computation", Step 2E says, in part:

"""
Otherwise, if the current node is a control embedded within the label of another widget, where the user can adjust the embedded control's value, then include the embedded control as part of the text alternative in the following manner:
...
If the embedded control has role menu button, return the text alternative of the button.
"""

It seems like this should simply be omitted, since we're hardly going to recursively call into the text alternative computation at this point; we've either returned its `aria-label` or `aria-labelledby` or native markup text alternative already, or else we'll pick up the contents in step 2F.