This is employer dependent in the US, too. I can Slack my boss and say “I’m feeling under the weather, going to unplug and rest today,” and she’ll say “Okay, no problem, feel better!”, and that’s the end of the conversation. Definitely the exception to the rule, though; I think OP’s situation is much more common.
There was a post some time ago where someone mentioned going to the doctor for an employer-mandated sick note and the doctor was so irritated by it, that they wrote the note demanding 3 days of bed rest, rather than the 1 that had originally been requested. Thought that was pretty classy.