Architects should pay their bills on time, just as they expect their clients to do so.
Send in the Cabe Design Police
With respect, a stub stack does not necessarily have to have an air admittance valve fitted. It can be fitted with screwed access plug. Such an arrangement is subject to the limitations noted in the article. If an air admittance valve is fitted however, the stack becomes a "ventilated discharge stack", according to AD H1 1.33, so overcoming many of the limitations of a stub stack.
If architects were paid what they are worth, this would not be an issue.
Mr Scruton puts me in mind of Frank Zappa's Central Scrutinizer in both name and deed.