It appears you may not fully understand their "machine." So let's engage in some theme park technology 101. Specifically, one of the most critical rules, which is
the law of capacity (number of guests the attraction can handle per hour). The cardinal rule there is
the highest capacity attractions employ continuous moving belt technology: think Haunted Mansion.
That is why Universal smartly designed Harry Potter to use that approach: a continuously moving busbar belt, but one that goes
far beyond the HM. HP's "very small"

four person ride vehicles are each mounted on KUKA robotic arms. As each unit travels through the attraction, it encounters a mix of massive animatronic sets and multiple huge wrap around screens, where the action of the robotic arm is coordinated with the imagery/routines.
And what Universal developed is actually superior to the "batch" technology (think: Soarin' or Star Tours) you are enamored with on two levels : not just higher guests-per-hour capacity, but also
better viewing.
For on you mass "batch" seating approach, you run the risk of having someone in front of you obstructing your view (which is why many people are so focused on getting the front center row on Soarin'.).
On Harry Potter EVERYONE gets the front center row.