What's the intended function of the previous functionality? Didn't double-tapping zoom in and out to a specific section? What problem does the delay solve that isn't present on unscalable viewports?
The delay allows webkit to detect a double tap. Otherwise, any element with a click handler would immediately fire, effectively disabling double tapping for their region.
That sounds interesting at first, but then what happens if say, the element takes you to another page? Then you'd have to go back a page, which would be a clunky experience.
What if it sends an AJAX request? You can't exactly undo them. The browser JS environment is sufficiently complex that "just undo"ing something seems like it would be... complex.