I wouldn't exactly call that secure disposal. Yes, the factory reset is the bare minimum. But you can probably still recover data off of it. To really be secure you have to run a wipe on the memory and storage. I would be interested in articles covering how to do that for phones and IoT devices. It's trivial to do on a computer, but much harder on other devices.

Nothing beats a hydraulic press for (s)IoT's [1] and all other electronics. Make it thin as paper then feed strips of it into a blender, pour the resulting dust into a batch of clay and make a IoT phallic statue with a placard "My Sensitive Data" for a viral TikTok video. One less thing in a landfill.

[1] - Shite Internet of Things

Interesting. If I get hold of someone else's device I am terrified what I might find on it and factory reset it before I do anything else. And being a tinkerer everything is taken apart and what I can't use goes out as components.