This isn't standardized, but matches what VTE does.
IIRC, I researched that issue when I submitted the DECSCUSR diff; and the current behaviour matches the VT510, VT520 documentation and the XTerm implementation.
And I went with the logic that matching the VT docs and XTerm behaviour is a safer way of implementing this, as the main consumers of such features are terminal apps like vim, which, AFAICS, tend to implement those features based on XTerm (as the de-facto terminal emulator out there).
So, in my mind anyway, this makes things easier for those apps, as they wouldn't have to add special workarounds/quirks for Konsole.
Yeah, the current way is fine, but I started using it in my own application, and I missed a way to just reset to the original state.
And ref. the linked discussion in the gnome bugtracker for gnome terminal/vte, the doc is a bit ambigous, so they chose to interpret it in a way that also enables applications to easily reset the cursor style.
And ref. compatibility; this patch makes konsole more compatible with gnome terminal (and the other terminals using vte).