100% correct.
As long as people can make FP+ reservations in advance and not be in the park when they make them, there is no workaround for this. The system cannot differentiate between a person who makes a FP+ reservation 7 days in advance for 10:00-11:00, and enters the park at 10:55 and uses the FP, versus the person who makes a FP+ reservation 7 days in advance for 10:00-11:00, and never enters the park. The system cannot "cancel out" that FP slot until 11:01 whether the person is in the park or not. And by 11:01, it is too late to go back and fill the slot.
The only solution would be for the system to keep track of people who make FP reservations and who do not redeem them. Do that too many times and they could take away your privileges. Disable your
MDE account or disable your MB.