According to the forum posts, it's happening to everyone who uses the default plug, the extension that comes with a 3 pin plug resolves the issue.

I have one short and one long cable, and am only just now realizing the issue. I'd simply assumed the short one was a fake I'd gotten.

Can't speak to why your iPhone and iPad do the same thing, I've experienced it when using sketchy cheap lightning cables or wall adapters (including ghost touching), but not when using better built stuff (like AmazonBasics or Anker).

That's assuming that your house have grounded sockets. My house does not and most of old houses in my country are the same, only new houses have ground.