The weight limit of the model being used is around 220 lbs, and it struggles to handle that. Most Americans that you'd call obese wouldn't be able to use these. The model (Xiaomi M365) was originally designed for Chinese consumers (who tend to be shorter/weigh less).
Yes that is the official weight limit, but speaking as someone who has one and weighs 20% more, it works totally fine.
Not sure why you think it struggles - even with the official firmware it easily and quickly gets up to 16mph. Sure you get a bit less range than a lighter person, but the difference isn't huge.
