Evidently the kinds of people that can't be bothered going into the Advanced Configuration Settings page would be confused by an additional item in the Advanced Configuration Settings page.
I never used the backspace button for back (though it's probably what's mapped to my mouse button #8 - I'll know on the next upgrade), but I did get mightily annoyed by two changes a while back, and am always happy to bring them up whenever there's a story about Chrom* devs doing this kind of thing.
1. snap-to-mouse - while dragging the scrollbar, if you move the mouse further than ~80 pixels away from the scrollbar column, the page jumps back to the original location - apparently MS Windows users love this feature, but chrome/chromium is the only application I've found on GNU/Linux that does this, and
2. clicking inside the URL bar selects the whole contents - apparently MS Windows users are used to this feature, but chrome/chromium is the only application I've found on GNU/Linux that does this.
No idea what the defaults are for OSX, and, really, it doesn't matter - these features should be sensitive to extant defaults on whatever desktop environment the browser finds itself running on.