I've seen the numbers reversed quite a few times, many in the vB4 forums but not so much the vB3... I'm on these forums as a friend once said "methodically" though and at any time of the day on any given day so don't be surprised.
You included a screenshot of the discussion forums, that could be related to searches being performed although so could the modification forum views but for example here is a screenshot of those currently viewing mods:
Although it's a different area entirely it does show logic different than that you have come to use so it's truly dependent on a few factors including time of day and the area of the site.
I will say this though, it seems the larger sites are still on 3.x more so than 4.x but that's imo.