The unintended consequence of virtual lines is that people need a window to return and some won't return. Which is math no one seems to have figured out yet - as seen in the spike of FP wait times throughout the day at various rides.
Tapu is more fluid in that it's not promising a specific return time - from what we can tell, rather works like a restaurant and pages you - but how long do you have to return?
In a traditional park each slide of a group of 4 racers at most has a 5-10min wait. Why bother with tapu on those?
Will they?
If they don't tapu everything, those slides will get overloaded as people try to slide while virtually waiting in line to slide.
As for the the non-returners, I'm sure they can figure a system that tells the computer that people missed their window and they need to either speed up everyone's return times or just pluck a few random people for immediate times to fill the gaps. I'd say the bigger issue would be the slowdowns from people who get to the top and take more time for whatever reason. Then they have to back everyone's wait times off to prevent over queueing. The question is how much queue do they anticipate holding on these rides. There has to be some to maintain capacity, but too much and people complain about false advertising. It'll be computer controlled I'm sure, but it's an interesting dynamic.