There is the "comfort level" aspect to this as well. Most motorcycle folks are not be comfortable doing "stoppies" or "2-wheel drifts" on asphalt, but these are none the less valuable skills. But - moving along a public motorway can be achieved in many ways. The good sailor "Avoids the storm he cannot weather and weathers the storm he cannot avoid." Most of us geezers here plan our routes & trip times to conform with our skill/comfort levels. We knowingly try to increase the probability of successful outcomes to ourselves by our prescribed behavior.
To be proficient with the hardware you use depends on your interest, physical ability & situation. There are always going to be conditions beyond our ability to respond properly, the only option is to anticipate & attempt to avoid those. Reflexes, eyesight, balance & coordination all decrease with age. Eyeglasses, hearing aids, really good tires & brakes, specialized training, all are ways we can minimize risk. You don't have to be a "young tiger" to make it point to point over the public road, just pick battles you can win.
Your point of learning to "fly the chair" is well taken, and a good skill to possess. Adding a bit of weight to the chair is an attempt to "standardize" the response of the hardware, the mass is then relatively constant and thus it's response more predictable. Physics tells you that the empty hack response vs. loaded is necessarily going to be different. There's no harm in skewing the odds in your favor by standardizing the hardware response. There is also no argument against consciously & deliberately training yourself to "stretch the operating envelop" of your hack skills by learning the "flying response" of the chair in a variety of controlled situations, as well as the
braking response. That's how you grow your skills, by deliberate, focused practice, not in the middle of a random, full-on-panic situation.
As far as losing speed by adding chair weight, this is a hobby activity, so speed is irrelevant. It's all personal preference, there are no points to be awarded or lost...
Except at the race track...which the public roads are not. Your primary job is to get your hardware over the road, the best way you know how, with your skin intact & not causing a problem for those around you. "Looking Good!" is entirely optional...