I say this as someone who did enough weightlifting to be in the overweight BMI range with a low percent of body fat (no steroids involved). Trust me when I say it’s a lot of work to get there. It’s not a category that includes a lot of people or invalidates the measure.
I know very fit people that still fall well in the BMI 20-25 range. Most around 23. You have to be very focused on natural bodybuilding for years if you want to become an outlier on BMI.
Or some combination with being super short or super tall. But this again affects a tiny minority.