It does. I have seen that on my browser. Firefox 24.0
Do you mean this board does? I have seen it a time or two, but in general when you click on "New Posts" the only threads that come up are ones that have a new post since your last visit. The SV board shows you older threads too, below that divider. The other nice thing is that it's not limited to 100 threads, so if it's been a couple of days you don't miss anything.
The behavior doesn't seem to be browser-dependent, it acts the same for me under FireFox, Chrome and IE.
'07 DL650, '01 DR-Z400S, '99 SV650 (race bike), '80 GS1000S, '85 RZ350, '08 Ducati 848