Vlad It was a default behaviour in previous macOS versions to move between system elements with Tab and Shift + Tab. Now they removed this by default, but you still could access this.

I don't thing this is something special; the features like this are little QoL improvements: they don't make browser any heavier and they don't clutter the interface though the person who used it in previous browser will likely to land here and won't be thinkinking about switching to something else.