I see this all the time, city inspectors don’t go into attics. I would call out the lack of supports. There should be some type of support at every elbow. I would also call out lack of sheet metal screws. It is recommended by every B vent manufacture and may be in your code.
These are from the installation instructions for B vent 6 inch and under. Two separate manufacturers both recommend sheet metal screws. I call it out every time I see it installed without sheetmetal screws. High winds in my area (or any area) can push on a B vent and twist poorly supported fittings and connectors in the attic space.
I noticed in the tables that the laterals given are never longer than the height. Judging from the OP’s picture, his lateral may be significantly longer than the height. This seems like a concern to me.
I agree Ryan I noticed that too. The best thing for the OP to do is to just call it out for repair by a licensed HVAC contractor. Lack of proper supports, recommended sheet-metal screws are all of a concern.
If the b vent in the OP pic was properly supported, I would not call out missing screws – we don’t have 100mph winds inside our attics here. If tornado makes a landing inside that attic, the screws won’t do much good anyway. As you know, the liability here is high, if it was common for these b vents to come loose, they would all indeed require it.
If that’s where you got it, then refer to the instructions. The diagram you posted shows you where and how to do it if needed. It is your choice to believe all b-vent manufacturers recommend them, I’m not here to stop you