Orphaned water heater today

Water heater at today’s inspection was orphaned 18 months ago. No signs of any issues, but still doesn’t seem correct. Transitions to a 6” as it makes a 90 up the. 8” pipe runs vertically 2 stories up through the roof.
Would you refer this to be evaluated by an HVAC contractor or am I off base on this?

A picture would make more sense.

I can see your concern/questioning. 8 inch piping up 2 stories would likely be too big for a conventional draft water heater. How much chimney was exposed in the attic and up above the roofline? Does your area get cold?
If you don’t see any issues with it, it was drafting properly, etc., I just make note of it and say something along the lines of verifiying with seller that it was was accounted for at the time (preferably documentation) or to have further evaluated to determine if chimney is properly sized. There’s a lot that goes into play when determining the size, so this would be a wise “further evaluation” recommendation, IMO.