What if the guy who is desperate to wee is not directly facing you? Maybe he's facing the guy on the other side of you. Could you have a 50% chance of getting your trousers wet? Would that make a difference to you?
Sunny-dave, what you heard is not an anology. An anology is a comparison between one thing and another usually to provide some form of clarification. What you have heard is an attempt to attach some form of reasoning to the situation and regretfully, the tale falls outside all the known types of reasoning.
Is this guy so nonchalant that he wouldn't think twice about emptying his bladder contents all over you rather than finding somewhere less innoffensive to do the job?
The fact that he "can't hold it in any longer" would not stop him from looking for somewhere else to empty his bladder in preference to you no matter how desperate he is. Consider that just maybe he would have the decency to empty his bladder elswhere.
If you are happy to transfer your logic regarding the guy with the weak bladder to the need to wear masks, that's great. All the same, given that your arguments are flawed and uncertain in the first section of your post, there is no certainty that the two assertions you claim at the end of your post are correct.