I took a very quick look at the iPhone capture. I don't see any notable issue (which is expected since this is "working" behavour), and the main noticeable item in the comparison is an apparent lower latency to the server. This appears to match the speculation I saw in the updates as well.
One thing you might be able to try, if you're able to change the APN on the hotspot, is to see if you're able to connect with a different APN from the consumer side. This is pure speculation, but what some carriers do is use a different APN for their business services, that will route to enterprise only packet gateways. Some carriers may not necessarily disable access to the consumer APNs though that might go through a different P-GW that's closer to you. The iPhone looks like it's using a path about 120ms shorter than the hotspot. And just by chance, going through a different P-GW you might hit different traffic shaping equipment or configuration.
Edit: although be aware that the carrier could also charge different APNs separately. I have no idea what AT&T does.
I considered switching APNs, but didn't want to run afoul of any AT&T rules.
I went ahead and gave it a try anyway, switching from `broadband` to `NXTGENPHONE`. I wasn't able to authenticate with `NXTGENPHONE`, so I switched it back to `broadband`.
After re-authenticating, I'm no longer being throttled. I'm both happy and deeply dissatisfied with this outcome because I think now I'm less likely to get to the bottom of it.
I'll add this to my updates and keep monitoring the situation.
You're welcome. This just reminded me of the IT Crowd... Have you tried turning it off and on again.
By disconnecting / reconnecting by trying the APN switch, it might've just put you on a different P-GW that has a different traffic shaping configuration or current state.
The only way to get to the bottom of this is probably just applying for a relevant job at AT&T, get accepted by whatever means necessary (low asking salary, nepotism, etc), check their network configuration yourself, then immediately submit your resignation once you're satisfied.
I think I read somewhere about someone who did exactly like this in a software company. A new employee showed up, immediately fixed a long-standing bug, then submit their resignation.
I took a very quick look at the iPhone capture. I don't see any notable issue (which is expected since this is "working" behavour), and the main noticeable item in the comparison is an apparent lower latency to the server. This appears to match the speculation I saw in the updates as well.
One thing you might be able to try, if you're able to change the APN on the hotspot, is to see if you're able to connect with a different APN from the consumer side. This is pure speculation, but what some carriers do is use a different APN for their business services, that will route to enterprise only packet gateways. Some carriers may not necessarily disable access to the consumer APNs though that might go through a different P-GW that's closer to you. The iPhone looks like it's using a path about 120ms shorter than the hotspot. And just by chance, going through a different P-GW you might hit different traffic shaping equipment or configuration.
Edit: although be aware that the carrier could also charge different APNs separately. I have no idea what AT&T does.