I ride scooters, motorcycles and a bicycle. I completely disagree, the front brake should absolutely be on the right side on scooters. On bicycles it makes no difference but I have considered swapping mine to front brake on the right side.
So why should a scooter have the front brake on the right side? For one thing an lot of scooter riders also ride or rode motorcycles and it could be confusing.
More importantly. The rear brake on a scooter is typically more important than the rear brake on many street motorcycles. Scooters tend to have a lot more weight on their rear tire than motorcycles. They also tend to have less powerful brakes than motorcycles, not always but often.
So, when you first start to brake on a scooter, your rear tire has more traction and potentially more braking force. Many scooters with front and rear disc brakes have the same size disc front and rear.
As you brake weight will shift to the front wheel and it now has the greater breaking potential. Most scooters do not have the braking power to shift weight to the front tire as some motorcycles do. On a sport bike or super moto you can do a "stoppie" and shift all of the weight to the front tire.
Anyway, a common cause of accidents is grabbing the front brake to quickly and sliding out the front tire. Many people like to start braking with the rear and then applying front as weight shifts and front tire can handle the braking force. I like to apply both at the same time and then squeezing the front harder as weight shifts forward.
I have only owned one scooter with a rear drum brake and it worked pretty good. My Like and Majesty both have front and rear discs. They would take much longer to stop if I used only the front brake. Yes the front brake is more powerful but the rear brake is still very important. My Like has a combined braking system so when I apply the rear brake it also applies some front brake. I don't like the system but it does make that left lever more powerful than the right.
Putting the front brake on the same size as the throttle is better in that you are naturally likely to roll off the throttle as you grab for the brake.