This lightweight solution worked for me:
function my_acf_render_field( $field ) {
if ( did_action('acf/render_field/key=field_508a263b40457') % 2 === 0 ) {
return;
}
echo '<p>Some extra HTML for the post object field</p>';
}
add_action( 'acf/render_field/key=field_508a263b40457', 'my_acf_render_field' );
Using the modulus division operator, the function will bail early every 2nd execution.