Put another way: if you assume 16-passenger shuttles, you have to have 26 second headways between cars in order to meet capacity.
If you don't split the track to allow unloading, you have 26 seconds to disembark 16 passengers, embark 16 more passengers, and then clear the platform in enough time to allow sufficient safety margin for the car immediately behind you. Station dwell times (essentially the time from train is fully stopped to time it starts accelerating, and therefore not including the last bit) are upwards of 30 seconds and much likelier to be close to a minute, which can't be done in sufficient time. Especially because full capacity cars generally require more time at stations, and I have to imagine that modified Teslas that can fit 16 people aren't going to be quick to navigate.
If you have multiple platforms at each station to accomodate the long station dwell time, maybe it could be done, but I suspect that it'd blow out their construction budget because of the extra space needed.
If they have to have multiple platforms at each station anyways, it might make sense to essentially have three lines - A<->B, B<->C and A<->C, instead of A<->B<->C - and only run direct. At least in that situation everyone would be getting off at each stop, which could simplify some things - and it naturally splits passengers into two platforms.
That sort of routing is also significantly improved by having smaller, independent vehicles (well, once the number of stops goes up) - sort of like the Personal Rapid Transit setup at WVU. [0]
If you don't split the track to allow unloading, you have 26 seconds to disembark 16 passengers, embark 16 more passengers, and then clear the platform in enough time to allow sufficient safety margin for the car immediately behind you. Station dwell times (essentially the time from train is fully stopped to time it starts accelerating, and therefore not including the last bit) are upwards of 30 seconds and much likelier to be close to a minute, which can't be done in sufficient time. Especially because full capacity cars generally require more time at stations, and I have to imagine that modified Teslas that can fit 16 people aren't going to be quick to navigate.
If you have multiple platforms at each station to accomodate the long station dwell time, maybe it could be done, but I suspect that it'd blow out their construction budget because of the extra space needed.