Using macos on low memory regimes will make it use disk-based swap.

For example, a Macbook Neo (so in theory, something with around 4GiB of free RAM lying around) might eat around 900GB of writes a day while not doing much at all, because it's basically on low on RAM and swapping all the time.

I don't know actually. I'll check haha. My best guess is it isn't.

Reading causes insignificant wear ("read disturb") that likely isn't a problem, but I don't think it's possible to issue pure reads to modern SSDs. The NVMe spec mandates tracking the amount of data read, and this has to be written to the drive. I'd hope the firmware buffers this and writes it at low frequency, but on the other hand, I doubt the firmware was tested in extreme random-read regimes. Unexpected failures from excessive statistics recording could be possible.