Missed my point.
Per the Hourly Capacity resource from
@MisterPenguin the Theoretical Hourly capacity of Test Trak is 1200 guests an hour according to the Hidden Magic category.
The Operational Hourly Capacity is 1,080 guests an hour. So while theoretically, Test Track can handle 1200 guests an hour, in reality, it's only getting about 1,080 guests an hour.
If we assume Genie+ allocates half the real-world throughput to Lighting Lane, that's 540 guests an hour that can experience the attraction using Lightning Lane. Because Lightning Lane always takes priority (they will dump the queue and go to an absurd ratio if it gets too long) and has a fixed distribution, we can take out the 540 from the total 1,080 guests riding an hour.
This leaves another 540 guests riding.
These 540 guests will be a mix of both single-rider and standby, whereas the original 540 was only Lightning Lane.
Assume 90 single-rider guests ride per hour (one per two vehicle dispatches on average), which leaves 450 standby guests to ride. In my experience at Test Track, 90 single-riders seems like a low estimate.
Alternatively, if we did not have a single-rider line, the total number of guests riding per hour would be 990 guests. As you can see, single-rider increases the operational capacity of the attraction.
That said, if we assume the same Genie+ Lightning Lane ratio where half the capacity goes to Lightning Lane (usually it's more than half), then 495 Lightning Lane guests can ride per hour and 495 Standby guests can ride per hour.
So assuming a ride like Test Track and Frozen have the exact same throughput (most the data online estimating capacity comes from someone standing at the exit and counting people) Frozen's standby would have a higher hourly throughput when compared to Test Track if they are running the same ratio.
I'm not advocating for the removal of single-rider, but simply explaining a component of Test Track's (undeserved, imho) high waits. A counter-point could be that the single rider is removing guests from the stand-by line, but, personally, I have never even gone through Test Tracks single rider line since it's never short enough for the experience. Without the single-rider line, I simply wouldn't ride Test Track unless I had a Lighting Lane. Even if we assume 100% of singles would've gone in Standby, that would just return it to normal throughput split.
My whole point is that the way we look at capacity (total attraction throughput) and the likely way Disney looks at attraction throughput (total attraction throughput) does not account for single-rider before determining their Lightning Lane distribution, hence shrinking the pie for Standby throughput.
Once again, it's awesome that they have single-rider at Test Track, but the attraction's overall horrid capacity, likely ILL ratios, and single-rider component, means that the normal standby line has a very low throughput, contributing to high waits.