I’ve seen one of those combo things in my entire life. They’re awful but certainly not common. The front loading machines allow you to have the machine inset under a kitchen counter which is a common place for them in the UK. Separate “laundry rooms” aren’t common and neither are basements so the machine needs to fit in other use environments. I used top loading machines for a while when living in Canada and had constant problems with the detergent staining clothes.

Regarding the sizing again, I’ve never had a problem. I’ve also never heard of anybody washing a comforter (although I don’t call it a comforter so maybe I’m misunderstanding what you mean). A comforter (or duvet) has a cover on it and you wash the cover.