--simplify-merges returns too many references

I thought I understood the intent of the various history simplification switches, but maybe I am still confused.

In git.git, I see three commits which touch stripspace.c:

$ git log --oneline -- builtin/stripspace.c 497215d Update documentation for stripspace c2857fb stripspace: fix outdated comment 81b50f3 Move 'builtin-*' into a 'builtin/' subdirectory

With --full-history and also with --dense, I see the same three commits:

$ git log --full-history --oneline -- builtin/stripspace.c 497215d Update documentation for stripspace c2857fb stripspace: fix outdated comment 81b50f3 Move 'builtin-*' into a 'builtin/' subdirectory

$ git log --dense --oneline -- builtin/stripspace.c 497215d Update documentation for stripspace c2857fb stripspace: fix outdated comment 81b50f3 Move 'builtin-*' into a 'builtin/' subdirectory

But with --simplify-merges, I see _more_ commits.

$ git log --simplify-merges --oneline -- builtin/stripspace.c 634392b Add 'contrib/subtree/' from commit ... 497215d Update documentation for stripspace c2857fb stripspace: fix outdated comment 81b50f3 Move 'builtin-*' into a 'builtin/' subdirectory 610f043 Import branch 'git-p4' of git://repo.or.cz/fast-export b4d2b04 Merge git-gui 0a8f4f0 Merge git://git.kernel.org/pub/scm/git/gitweb 98e031f Merge git-tools repository under "tools" subdirectory 5569bf9 Do a cross-project merge of Paul Mackerras' gitk visualizer

None of the "new" commits touches this file. The man page suggests that simplify-merges should result in fewer commits than full-history.

"       --simplify-merges
       Additional option to --full-history to remove some needless merges from
       the resulting history, as there are no selected commits contributing to
       this merge."

Am I confused or is git?

Phil