bookOutputName still gets "-1" suffix added to SVG file names

[Jeff Olson]

I've got to generate a thousand+ cropped SVG files with specified file names
from one lilypond compilation, so I'm wrapping each score in a \book with
its own \bookOutputName as in this MWE:

\version "2.24.1"
#(ly:set-option 'backend 'cairo)
#(ly:set-option 'separate-page-formats 'svg)
#(ly:set-option 'use-paper-size-for-page #f)
#(ly:set-option 'point-and-click #f)
\book {
  \bookOutputName  "Foo"
  { f' }
}
\book {
  \bookOutputName  "Abc"
  { a' }
}
\book {
  \bookOutputName  "Bar"
  { b' }
}

But the SVG files all have the extra -1 suffix as though there were additional
files from the same book that would collide:

  32 -rwxrwxrwx+ 1 J None   32199 Mar 29 22:25  Foo-1.svg*
  32 -rwxrwxrwx+ 1 J None   32190 Mar 29 22:25  Abc-1.svg*
  32 -rwxrwxrwx+ 1 J None   32231 Mar 29 22:25  Bar-1.svg*

My MIDI files don't have this problem since they only add a suffix on
**subsequent** files with the same base name, and there's only one per book.

These "-1" suffices are messing with my URLs for the SVG files,
so I'd appreciate any ideas on how to get rid of them.  Thx.

P.S. I get the same thing using 'backend 'svg
P.P.S  I'm using Windows 10 Pro with Cygnus bash and Frescobaldi 3.1.1

Jeff