When a room is booked for 2 pax, and some argued it actually makes sense to pay for the 2nd pax, instead of getting it free for the 2nd pax.

And when this lack of logic is being pointed out, apologists deemed the abovementioned as silly interpretation, and yet their illogical arguments are valid?

It is one thing to be an apologist. It is another thing to be illogical. If we paid for another set of breakfast, it meant that the hotel has unilaterally downgraded the room booked for 2, to 1 pax. And then forces you to top up again for breakfast. That is double counting.

If arguing having more breakfast provision (anything more than 1 per room) = quality of breakfast going down, apologists might as well lobby for 1 breakfast per room, regardless of no. of pax booked, or even better, removal of breakfast benefits completely.

Once again, if we paid a room rate for 2, we should get the breakfast for 2. If you want to be an extreme pedant, you could argue I need to register the guest. But if you want to make an illogical argument that on top of me registering the 2nd guest, I would still need to top up even when the room rate is meant for 2, then it is an out of point argument.