I understand your thoughts, but a lot of unknowns come into play. First would be that I doubt that you radon piping is installed with any particular slope, this in an extreme situation could reduce the proper cfm flow and possibly end up with a stagnant sluggish pile of goo in the pipe. The sub grade drainage suitability has been raised previously. I'm not familiar with what they use for pipe, fully slotted black drain tile may never "pool" water, but the white sewage pipes with holes on one side may depending on the orientation, something else that I don't know for a radon system.