I remember someone said that but I found that not to be the case for me - I have whatever WMP/WMC that comes with Windows 7 Ultimate.
EDIT - do you mean Wild Media Server? I'll check it out...
The Sony Bravia 2009 DLNA client
is sensitive to an additional Sony custom DLNA folder attribute indicating the media type of a folder and will only show a video folder from the video menu on the XMB, audio from audio menu etc. However I found during experiments I made with the PS3 Media Server source code and testing with uPnP Tool that it has no effect on the BD Players. Mezzmo uses these custom attributes too regardless of renderer but again no effect on BDP.
It's helpful to consider how DLNA works at a basic level - the server just lists folder contents and the client decides what media types to show you. If your client only shows you audio in the audio menu hierarchy that's not something Serviio can change. Nor can Serviio tell which parent menu on the device you're browsing from - hence the need to show all the media folders all of the time, which adds to the confusion. Clearly DLNA is not well thought out as a standard from a usability point of view but then I think that much is obvious

It's a shame really. TiVo managed to make a technophobe-friendly UI pretty much a decade ago but Sony and the rest of the DLNA consortium can't manage in 2011!