Water heater & boiler venting

Here are some photos from today’s inspection. Gas water heater Vents directly into the boiler vent. water heater attaches at the same level and is taped so I cannot see the actual connection. I want to make sure I understand if this is acceptable or not and why. I am thinking not.

Why are you thinking not?

Water Heater enters at the same level as the boiler and there is no wye visible (tape covers the connection)

This would be a case of undersized flue because the the two lines entering the chimney thru a 4 inch pipe, 3" and 4" I would recommend that the pipe entering the chimney be enlarged