Just because it says so in the CB manual doesn't make it right or wrong. That is the problem, people see pictures or read it on the net and think its law. It also says to follow all local and state codes, and to check with the other appliances manufacturer suggestions. There is no cast iron boiler on the market that doesn't void warranty if its ran unpressurized and it doesn't matter what CB approved treatment additive is put in. It has to be approved by both manufacturers. It is also boiler code that the vessel maintains a minimum pressure. Anytime a safety device is bypassed or eliminated it violates code. Also if you read the grundfos,B&G,wilo or taco warranty it does not cover cast pumps in open systems. Doesn't mean that they never have covered one, but thats exactly what their policy is. Thus why you see on some OWB part supply sites bronze and Stainless steel options.
No one said running a 2nd floor can't be done, but if you read the link you would see the problems that "could occur". I don't know about you but if any of these things went in on an install without the customer fully understanding the risks and options, then I can confidently say it was an unqualified installer. These are the very things that give them a bad rap. Anyone here check with the insurance policy, if a problem ever did occur and a forensic engineer has to be called out to find the cause, they can and will void or limit the claim loss of the HO policy if these conditions exist. Or they will go after the installer, and you hope he is licensed and insured. If he's not licensed he can't be held liable for his install, he would be treated as a handyman working under HO direction. So if the boiler does rot out and flood an area , hopefully its limited to less than 10,000 in damage. Each policy is different, but I can assure ,if you have State Farm this is their policy. We cleaned one up last year for SFarm and their remediation contractor was ruthless with expenses on the previous installers dime.
As far as that valve being partially closed, that has no effect on the boiler being pressurized. It is either an open loop or its not. All the installer has to say is you were aware, then its a he said/she said deal in court. If it wasn't inspected by the city then your on the hook. And no inspector would approve that. There are 1000's of jobs done without pulling permits and inspections, I guess that makes them all in good working order and done right too.
If you draw a line between plumbers,pressurized experts( licensed boiler installers), and yourself , its not good for anyone. You will always be ahead when you help each other out. Similar to you posting here, to help someone out. If a city official or inspector just dropped by during your install. Will it help you to argue & complain with him or to listen and discuss things so you both understand each other respectfully. Yes I know there are some that there is no talking to, but you'll never know if you don't try.