ice forming on roof via gas furnace vent

I inspected a newer home today and had the following concern.
The gas furnace and intake are located near the roof peak. The furnace was running and the vent/flue gases were exhausting or venting out of the plastic vent pipe. The problem was/is, the gases are condensing when they hit the cold air (20-30 degress, cold for Virginia), dripping down onto the roof surface, then forming ice. No leaking or ice formation was observed in the attic space. This does not seem correct. Has anyone else seen this condition? If so, what are your comments or concerns?
I noted the conditions observed, but I’m not sure if this can lead to problems. It just doesn’t seem right.

I’m am more concerned with inlet and exhaust being so close to one another .
I would pass this on ,Immediate ,further evaluation by qualified personal .

the clearance between the inlet & exhaust/vent was noted, along with the ice and condensation.

What Roy said

The supply and exhaust on the high efficiency, direct vent gas systems usually should be at least 12" apart but always check with the manufacturer’s specs.