What makes it broken, out of curiosity? Is there a spec anywhere that suggests that behavior is incorrect? Or is it just because it's not what Chrome does?
I'm personally getting a ton of mileage on the Safari's much more stable forward/back cache, the fact that you can go back reliably gives me more comfort than other browsers where going back usually refreshes the page (although I can't really explain how this is much better). I personally feel that this bug is more of a web app bug rather than the browser.
Of course, the exact implementation is not specified, browsers are free to either implement cached behavior, which I think Firefox does as well, or just a naive refresh.
https://html.spec.whatwg.org/multipage/browsing-the-web.html...
Which appears to be supported in Safari, just like all the other browsers.