It depends on your goals. 'Benefit on the body' and being a very good long distance runner aren't the same things.
If your priority is being the fastest distance runner you can be, then the Primal Blueprint approach to fitness won't be the best way at all. It doesn't try to be. PBF is more about supporting health and movement without undue chronic stress on the body.
I think for cardio to chronic it needs to be long enough, regular enough and intense enough that your body is almost always under some negative effect from it. A 30 minute run at moderate pace probably won't do you any harm if you're fit. If you're unfit and doing it is HARD work, and you're doing it daily, then it may be a problem.