Methinks that Tesla has put more thought into how folks will use urban charging differently than long-distance trip charging in the long run. The the current behaviors of how folks today use either type of supercharger may not match with the behaviors in the future.
We know that paired superchargers allocate capacity in quarters, so if there are two cars a 145kw charger will allocate 108kw-36kw, 72kw-72kw, or 36kw-108kw, depending on the situation. Really for the vast majority of cases, what we're simply judging is whether when the 2nd car arrives, the allocation behavior should remain at 108kw-36kw, or whether 72kw-72kw is better. But what is "better"?
Those are allocated capacity, not actual usable delivery, so anytime the 1st car is in a taper, 108kw->72kw, 72kw->36kw, 36kw->0, it is using less than allocated, and it is POSSIBLE that a 2nd paired car COULD use more of that bank of 36kw than the 1st paired car. We're all trying to judge whether it is more fair, or more efficient (in overall utiliazation, avg charge speed) whether to allocate 36kw to the car that arrived 2nd rather than 1st.
Consider this: in the regular (paired) superchargers, Tesla could probably trivially modify them to act more like urban chargers. I.e. once the 2nd car plugs in, use a 72kw-72kw split instead of 108kw-36kw - It's a very simple algorithmic change.Then it will act exactly like a urban supercharger, until one car unplugs. This alone would guarantee that paired chargers would always be as or more utilzied or efficient than urban chargers. - we only need to debate what fairness means in terms of wait time for each driver.
But Tesla didn't do that, and probably won't. Here's why. Regular superchargers were designed WHEN the problem was long-distance trips (how folks use them in urban areas today may be different). If the superchargers were designed with an ultimate spacing of 120 miles apart, then the first 40kwh dispensed is a matter of NEED, not WANT. You NEED that to get to the next charger or else you risk being stranded (or get into the range anxiety <20% SOC that should be for margin). Anything you charge up beyond that is more about WANT, rather than NEED. If Tesla assumes every car is on a trip, they are really trying to minimize time to get what you NEED, and then it's actually the taper, not the allocation, that's actually slowing you down for what you additionally WANT.
Urban supercharing is s diffrent scenario, and Tesla may be optimizing for some future where urban chargers will be spaced no more than say 20 miles apart, i.e. you're never more than 10 miles from the nearest one. But that also means that to go charge, you may have to drive 10 miles out of your way and 10 miles back, just to charge. That's like 20 minutes (at 60 mi/hr), more like 30-40, just in drivng time on top of 30 minutes of charging time.
Here's where I'm guessing Tesla has put the thought into the future - Instead of going about your days and waiting until you drop to 20%, and making a specific trip out of your way to charge, you'll do it when it's convenient, say when you happen to be passing by while going to the store one day. But that means it's opportunistic, and you can't always plan to be at 20-30% SOC, so more folks will be urban charging opportunistically at 40%, 50%, 70% SOC even. So more visits will not even be able to take advantage of 108kw, let alone 145kw, i.e. you're already in the taper. When you add that more batteries will also be cold-soaked, which can still be the case even if it's 60F outside but you've only driven 10 miles, even less chance of using allocation above 72kw. Predictability, if you go for a 20 minute charge twice a week on average, may also be important, i.e. you can predict about how much time it'll take to go 40%->60%, 40%->80%, or 55%->75%, before you even head to the supercharger, so you can judge whether it's worth your time today vs you might pass by one in another few days.
Now this is oriented for the true urban owner who lives in a condo or hi-rise or rental that has no provision for L2 charging. If you are urban and have L2 at home, Tesla is not designing urban charging for you. And if you have a long, urban commute where you need to supercharge every day on your commute, you're really trip charging on your daily that would fit more of the distance trip scenario, but there's less of you, so you're not the target design point for either scenario.
TL;DR: Urban charging is being designed for the future where it will be shorter, but more frequent opportunistic urban visits at higher SOC, more cold-soaked (not same as freezing) batteries. Less visits would take advantage of charge capacity above 72kw anyway, and now charge visit durations are more predictable too.
