GP was talking about how Apple does not force you to open links with Safari except in one case.
The situation with webkit is a different thing.
It's always Safari.
In a different skin, but it's Safari nonetheless.
Do Firefox or Chrome on iOS support web apis that Apple does not support?
No, they don't, because it's Safari.
Sorry if I skipped a few steps and went straight to the conclusion, that's why it probably looked off topic to you.
GP was talking about how Apple does not force you to open links with Safari except in one case.
The situation with webkit is a different thing.