Virtualdomains and tmda-filter

I try to set op tmda with vhcs incl. postfix and maildrop. I take "tmda-ofmipd 
+ VPopMail or VMailMgr" as point of departure. In it is written:

> The tmda-filter program has a command-line option for use with virtual
> domains.
>
> -S <script>
> --vhome-script <script>
>
> You give the name of the script that prints the virtual user's home
> directory as the argument to this option.


However, none of these options are mentioned in tmda-filter. But, in 
tmda-rfilter you find a number of options, among others: 

>    make_option("-S", "--vhome-script",
>                 metavar="SCRIPT", dest="vhomescript",
>                 help= \
> """Full pathname of SCRIPT that prints a virtual email user's home
> directory on standard output.  tmda-filter will read that path and set
> $HOME to that path so that '~' expansion works properly for virtual
> users.  The script takes two arguments, the user name and the domain,
> on its command line.  This option is for use only with the VPopMail
> and VMailMgr add-ons to qmail.  See the contrib/ directory for
> sample scripts."""),

Now, tmda-filter is a wrapper around tmda-rfilter. Therefore, I would expect 
tmda-filter to pass options to tmda-rfilter. But, as far as I can see, it 
doesn't. 

>    program = sys.argv[0]
>    execdir = os.path.dirname(os.path.abspath(program))
>    execfile(os.path.join(execdir, 'tmda-rfilter'))

Have I misunderstood something? If I am right, shouldn't tmda-filter be 
rewritten in order to preserve options?

Flemming