bug#36145: 26.2; Unable to "trigger another backtrace"

[Xu Chunyang]

(info "(elisp) Using Debugger") says

> When the debugger has been entered, the ‘debug-on-error’ variable is
> temporarily set according to ‘eval-expression-debug-on-error’.  If the
> latter variable is non-‘nil’, ‘debug-on-error’ will temporarily be set
> to ‘t’.  This means that any further errors that occur while doing a
> debugging session will (by default) trigger another backtrace.

Text before "This means.." is correct, but the conclusion seems
incorrect, to reproduce

- emacs -Q
- M-: (/ 1 0)     ;; enter the debugger
- M-: (/ 2 0)     ;; just message the error, no another backtrace

Am I misunderstanding "trigger another backtrace"?