Documents relating to proving his common law relationship are submitted to IRCC directly, what does that have to do with his current residence in the UAE and the risk of exposure there? This information is not shared by IRCC with foreign governments especially when they know the prevailing laws there prohibit same-sex relationships, this information is stated in the privacy laws that IRCC has to strictly abide by.Does IRCC not check marital status and validity of marriage certificates from the country where you got married? Does it not check to see if the marriage has been annulled?
Similarly there is a process for checking common law partners' status - or conjugal partner status - which is more likely in this case.
But do you have any idea what the actual process of confirming it is? Do you know how questions are asked and what information is shared?
Provide the evidence so that this person can take an informed decision - please dont state personal opinion or anecdotal evidence.
This forum is based on people helping others with their immigration queries, it's never been a substitute for legal advice provided by a lawyer. I think people realize that, i'm not sure why you think this needs to be highlighted several times.
I'm the first person to tell someone if their query is too advanced for people here to answer, and that they need to consult a immigration lawyer. This however is a very straightforward query.