I might chime in as a voice of dissent here. Clearly many people would prefer this interaction but one of the main things I value in Orion is "it's Safari but better", adhering very closely to Apple's HIG & macOS conventions. Chrome & Firefox (and their ilk) seem to have made the deliberate choice not to try and appear native within macOS and these navigation gestures are just one of the many places that shows up.
For those who don't like the native gesture because of the perceived slowness, the ⌘[ and ⌘] keyboard shortcuts or long/right-clicking on the next/back arrows seem like much better ways to accomplish e.g. quickly moving back 5 pages as one of the examples in this thread has than using gestures, without impacting the most common case of going back/forward a single page.
I hate suggesting "just add another option" but I would hope should this change get implemented those of us that prefer Orion's native behaviour have a way to preserve that. I also value that it makes it very clear you're performing what can be a destructive action by having the whole page move rather than a comparatively small arrow peeking out from the side (in some of the mockups proposed here it's less than 1% of the window area which seems very easy to miss), and allows you to quickly peek to refer back to content on the previous/next page without losing the current page.