I wondered about that when we got our new 60" slide in range, and yes, I have had splatters land back there. So far, I've been able to remove the grates over the burners, grill, and even remove the griddle to get back there more easily to clean the top of those vents off pretty easily. I can get a thin damp rag and kind of slide it behind the vents to get at the bottom part of my ceramic tile backsplash too, though I only do that when I'm doing my major cleaning when I clean under the grill and the baffles in my vent hood too... I aim for once a month but if I'm honest it only happens like every 6-8 weeks, LOL! (We have a larger family and I cook a lot... I don't use the grill often and I clean that out thoroughly every time I use it, but I don't have a cover for it yet, so even sitting unused I have to clean it out periodically because stuff falls in there.)
I haven't gotten inside that oven vent area though. Honestly, I haven't tried.

I don't think it's a magnet for stuff (since my prime ventilation is an overhead range hood), but I do occasionally get splatters. A damp cloth on a pointy thing (I wrap it around a chopstick) can get between the vent holes on my range.