Trust me, the page has been amended and is now clearer. You can see the previous version at https://web.archive.org/web/20260619195853/https://tfl.gov.uk/fares/free-and-discounted-travel/60-plus-oyster-photocard although the stupid cookie message gets in the way a bit.
The National Rail services that don’t accept the 60+ Oyster card are HEx and HS1.
The linked map also explains the situation accurately, apart from a spurious column about disabled freedom passes.