The weight on the bar is always constant. The author is trying to explain the amount of force required to overcome the weight falling down and then accelerate it upwards. The 275lbs was given as an example of an amount of force used to overcome a 135lb weight. The force you apply has to be greater than 135lbs because you decelerate the bar and then accelerate it upwards. For simplicity, if you applied constant force, which results in constant acceleration applied to the weight, the time it takes to travel a certain distance can be calculated. You can use the equation below assuming constant force/acceleration:
(Force - Weight) = acceleration x mass = (2 x distance)/(time^2) x mass
Using the author’s example, lets say you applied a 275lb force (1223.3N) to overcome the 135lb weight (600.5N) over a length of 0.5m from the bottom position to the top position of a clean. We’re able to calculate exactly how long it takes if we assume constant acceleration:
(1223.3N - 600.5N) = (2 x 0.5m)/(time^2) x (61.23kg)
=> time = .3136 seconds
You can manipulate the equation however you like to solve for one variable. All the author is saying is that it requires more force than the actual weight to overcome it’s inertia or momentum and accelerate it. If you had a 135lb weight and picked it up slowly, you would apply less force and generate less power in comparison to if you picked it up as quickly as possible. It sounds like the underlying message the author is trying to get across is that you control how much force you generate and it is not equal to how much weight is on the bar. You could apply the concept of maximum power output to your training. I remember reading an article in the past couple years about some device that could be attached to a barbell to measure power output. That way, it doesn’t really matter how much weight is on the bar, only that you’re training for peak power.