This feels a bit like how Esc was nerfed over the years in Firefox and others until it essentially did nothing. It used to mean STOP. All sockets were closed, the page stopped loading, and I think way waaay back, even animated gifs stopped cycling and JavaScript timeouts and intervals were cancelled. Single-page webapps were the death of Esc, it was too confusing to users to have a page suddenly hang because they pre…
Ironically, that's probably the reverse of reality. Looking at the comments here, for starters, we have people espousing views that things have "always" been this way, and quoting their experiences of "the past ten years". It's the young people who are having problems and need to be re-trained here.
The "old timers" will, conversely, have experienced data entry on terminals or in MS-DOS programs like (say) Borland Paradox, where of course things like a backspace key will at most have moved from field to field on a single page, if indeed it caused inter-field motion at all. (The CUA Guidelines give no indication that autotab applies to backspacing from the first field position, i.e. auto back tab. There's a COMPSEC83 paper that talks about it, though.) Backspace certainly didn't switch forms.