Accurate to a degree because the cam lobe controls the valve and its rate of opening and closing and where does it on the lobe. The lobe can slow the valve down. And that’s what it does. Earlier fast rate cams had the problem you think they have. It is all in the valve spring to control most of the action. Since valve spring tech wasn’t what it is today during the advancement in aggressive cam lobe profiles 30-40 years ago, the cam got the blame. It is partially true due to the cliff the lifter fell off of & lack of spring to keep it closed. Modern profiles slow down the losing rate at the last little bit.
Remember it is the springs job to keep the lifter on the cam lobe. The job of closing the valve is second banana. The valve train can be made super light to make the job easier. And it is done when the need comes into play. And when ignored, the springs wear out. This is evident in drag racing. The higher the performance, the more often the valve spring is changed out.