Screen reader issue with tab blocks

Thanks for your detailed response and careful research, Marvie! 

I did my testing using VoiceOver + Chrome, so perhaps that's the root of my issue. I understand that VO works best with Safari, so perhaps there are some compatibility issues between VO and Chrome that affect this. I'm relatively new to testing with screen readers, so it's useful to know that in a variety of situations this text is read as expected. I may need to rely on learners who use screen readers being familiar with issues like these and making their own choices around reader + browser combination to mitigate them.

Many thanks.