cautionary accidental styles with doubly altered notes

Dear LilyPond developers,

the accidental styles piano-cautionary, modern-cautionary, and
modern-voice-cautionary don't seem to work correctly with doubly altered
notes, cf. attached example:

If d flat follows d double flat in a different octave or on a different
staff, the accidental is printed in parentheses. The same holds for
sharps instead of flats and for other notes instead of d.

To my understanding, the single flats and single sharps, resp., should
be printed without parentheses, because they are essential: omitting
them would change the pitch of the note. Please correct me, if
I'm wrong.

Moreover, placing an exclamation point after the note does not remove
the parentheses. This may be related to
https://gitlab.com/lilypond/lilypond/-/issues/2810

Best regards,
Helmut