Yes. Winamp still cuts off all tag field contents at 00h bytes, regardless of ID3v2's unsync flag.
I think, unsyncing is officially deprecated by the ID3.org, as is the TYER field etc. (which I personally find silly as it's much easier to implement than struggling with ISO-style date values etc...)
Of course, it should be supported by Winamp and maybe you should consider posting that bug in the Official Plugins Bug Thread (pinned to the top of this forum).
Besides that, you could try mass tagging software such as MP3tag (
www.mp3tag.de) to try to convert all your tags to ID3v2.3 or 2.4, maybe also changing them to UTF-8 which is much more flexible (also for your cyrillic titles) than Windows codepages are. MP3tag should also automatically remove any unsyncing bytes and flags.
Best regards,
kzuse