Windows-version dependent callback?

Hi,

my (unreleased) MIDI tests have spotted that not all versions of MS-Windows
seem to send out the MM_MOM_POSITIONCB callback/notification resulting from
a MEVT_F_CALLBACK event in midiStreamOut().  w9X/ME appears not to know about it.
Machines since NT honour it (even though I've seen mixed results about w2k).

More generally, I'm wondering whether Wine should behave similarly
based on the version setting in winecfg?

What is Wine.wisdom on this topic?

We've seen apps hang because of missing callbacks or notifications from Wine.
Perhaps an app receiving extra callbacks or messages that it does not know
about will cause as much trouble?

Thanks for your help,
    Jörg Höhle