Aren't non-rechargeable batteries still at least a little dangerous, though?

They're more dangerous. The reason lithium-metal batteries are "non-rechargeable" isn't that recharging them doesn't work; it's that they have an unacceptable probability of exploding during the process. Other forms of electrical, thermal, or mechanical abuse can have similarly spicy results.

Spare non-rechargeable lithium batteries are also forbidden in checked luggage[0]. AirTags are allowed because the battery is installed in a device, though Lufthansa briefly tried to argue otherwise after some bad press involving passengers finding their own lost bags[1].

[0] https://www.faa.gov/hazmat/packsafe/lithium-batteries

[1] https://arstechnica.com/gadgets/2022/10/lufthansa-awkwardly-...