Ah yes, I see how that could be confusing. I’ll have a think about how to make that clearer on here.
Travelcard vs caps is a do the maths thing I’m afraid. If you’re travelling before 0930 and going into or via zone 1 then the discounted travelcard is probably better. If you avoid zone 1 and/or only travel after 0930 then it’s unclear which is better.
And Gatwick is the same for railcard fares too. Even the 16-18 zip card isn’t as good if you have a 16-17 Saver card for National Rail, whereas it used to make quite a difference.