You may have that ability, but my point is, not everyone can handle that. It depends on age, body weight, experience, how fast you drink it, as well as how much you drink, and how quickly you get onto the ride right after you drank. Too many factors into the equation in my personal opinion.
I for example, never feel sick on FJ, but there are a lot of people on this forum that do without the help of alcohol. While Fallon's ride is nothing compared to it, people have the potential to get on simulators without alcohol and still get sick, or feel ill. So, having alcohol that accessible and close by just increases the chances of sickness and clean up for the Universal crew.
You are certainly entitled to your opinion. I am thankful to not have experienced being in a ride vehicle with an ill guest in many decades of visiting amusement parks (yea!).
Motion sickness occurs when one part of your balance-sensing system (inner ear, eyes, sensory nerves) sense that your body is moving but the other parts aren't.
People have different triggers, but you cannot definitively link motion sickness with alcohol consumption especially, when in moderation - such as i described: 1 drink, 15 - 30 min prior.
If anything motion sickness/alcohol connection is due to drinking copious amounts the evening beforehand.
Just because there's a beer cart/bars throughout the parks, doesn't mean the majority of guests avail themselves. Social drinking is perfectly acceptable in the parks. Security keeps a lid on things. If anything the stiff prices probably put the clamp on many who might be tempted to over-indulge anyway since they are on holiday.
Common suggested precautions can be easily found @ reputable online medical sources as follows :
1.
Don't drink large amounts of alcohol the evening prior as it speeds up dehydration and lowers your body's resistance to motion sickness if you are prone to it.
2. Drink plenty of water to keep your mouth moist
3. Avoid greasy or acidic foods in the hours beforehand, such as coffee, orange juice/grapefruit juice, bacon, sausage, pancakes. They are slow to digest, and in the case of coffee, can speed up dehydration. Better choices include breads, cereals, grains, milk, water, apple juice, apples, or bananas. Do not skip eating but do not overeat.