Mine do. But it's really not a problem. They're fighting fish, so of course they fight each other if they see each other.
Mine see each other in the divided but it's no problem. There was a tailbiting issue, but never fret over it. If there is a tailbiting issue (from stress from seeing a male betta and not being able to attack), the first step is to simply put more plants against the divider as a physical means of blocking. Or just let them deal with it (i did this and it worked just fine), or buy a whole 'nother tank.
As long as they don't REALLY get to each other, i don't see a problem. Mine just recently resumed tailbiting, but I love him anyways, so I simply make sure he doesn't get fin rot from it.