I guess the privacy advantage of a regular SIM is that as soon as you pop out the sim card out of your phone, towers can't track you anymore.
With eSIMs on the other hand, I can never truly trust that an eSIM is de-activated? Feels like you actually just have a permanent sim card in your phone and your phone can just be tracked no matter the status of your eSIM.
Or is this not technically possible?
One of the suspects in the Bali bombings was caught because while they frequently changed Sims, they didn't change devices. They were tracked by the IMEI.
That's correct. Iphones are especially vulnerable to that since they don't shut down all the way and always keep some radios enabled. Android devices will generally shut down properly.
But in any case, do you really need to worry about tracking by a carrier? Locating a phone is possible but not easy and usually only happens when it's specifically requested by the police.
If that's your threat level, you probably don't want to own a phone at all.
If a phone can track you with a deactivated eSIM then it can also track you without a SIM, by just also giving you a secret eSIM for use when your regular SIM is missing, and then simply lying to you about it.
The SIM is just an identifier. There's nothing particularly special on a SIM card, that's why the switch to eSIM has happened so seamlessly. So, you're right; it's totally POSSIBLE that an eSIM could stick around if you delete. But it's also possible that your phone could save the info on a SIM card.
For the record, I don't think that's likely. Your phone's operating system (iPhone or Android) is built by a different company than the carriers that presumably want to track you. I doubt they're secretly colluding with carriers, because Apple and Google (especially Google) have enormous business models built around tracking you, and profiting off your data.