But that means that they cannot force you to stay home waiting for a courier. He could've asked them for a return label to send it back. Refusing to stay at home for a day because of that is valid as it should constitute a personal expense (no lawyer).

Yep. He could have said "I'm only available to hand over the parcel to a courier on Saturdays 9am-5pm or during week days between the hours of 6pm and 9pm" and they have to figure out how to collect it in those hours - it's their problem essentially. And if they did take him to court they wouldn't have a leg to stand on, since he has shown willingness to return the item.

Yeah, threatening him with legal action was absurd.