Thanks for the link to https://sci-hub.mu/
I fail to see the strawman arguments that you mention again. The discussion is about the probability of animals having emotions and feelings.
Based on the structure of the brain and the receptors and the involved chemicals, it is very likely that all reptiles and all mammals feel pain. Even fish might have some sense of pain. Humans follow often the "intelligence" related to feelings (bad diet, lack of sports, depression, fear, laziness, procrastination, addiction,...). IMO it is very likely that animals that can learn are driven by (intelligence related to) emotions and feelings and not by some unemotional intelligence and will or a simple "mechanical" reflex.
Another quote from another article: http://veterinarycalendar.dvm360.com/pain-management-reptile...
It is very difficult to assess pain in reptiles and there are no standard methods or assessments available to assess the level of pain in birds. Therefore, you are left with past experience, observation and anthropomorphism (if I had a fractured bone I would want an opiate). Reptiles seem very stoic and do not cry out in pain. I vividly remember many years ago amputating a rear leg in a chameleon and upon recovery he was making a squeaking-type noise and had tachypnea. Despite having been taught that "opioids don't work in reptiles" I gave him morphine. Fifteen minutes later when he stopped making the noise and breathed a more normal rate, I became a convert and gave reptiles analgesics and became dedicated to study the effects of analgesics in reptiles.