We had a discussion about this some years ago: topic13121.html
My thinking is that male rabbits do have nipples but they may be so unobtrusive as to be missed. It doesn't seem logical that they wouldn't have any, since they are mammals.
If you really want to know, you could mark the kits that seem to have no nipples and see what happens later.
I agree with Maggie, it could be an indication but I would think checking there genitals to be much more accurate. I am curious how it turns out though so keep us updated