Really? I figured they would have more capacity. I kind of want to buy a set at some point so I can do my comforter too. My normal sized top loader will not take it as the agitator takes up lot of space. I can shove it in there, but it's so squeezed that it wont really clean properly. The only place I can clean that is at the laundromat which is kinda a pain, and expensive. Those washers remind me of the Street Fighter pin ball machine we had in college "INSERT ANOTHER QUARTER! YOU CANNOT WIN IF YOU WALK WAY!" except with loonies.
Though the front loaders do have the mold issue which kinda makes sense as by design some water will sit in it, but leaving the door open takes care of that I believe.
What I wonder is why nobody invented a washer/dryer combo yet. Basically the washer would be on top and when it's done it dropes the clothes into the dryer compartment and starts it, then you can go load a new wash load at your own leisure while the other load is drying. I should patent that.

I guess it's a cool idea in concept but in application it's a disaster waiting to happen. Top heavy, etc.
First, yes, the claimed capacity of top loaders is a bit larger than front loaders, sometimes. There are extra large front loaders, but remember, with a front loader, the entire drum capacity is useable, unlike a top loader. Fill a top loader with clothes to the top and you probably have clothing that won't wash properly.
We have a Whirlpool Duet Steam set of front loaders and love them. Cleans extremely well....surprisingly, in fact. I threw in several pairs of jeans I had almost caked with grease (playing in the junk yard does that sometimes) and figured, before I throw them out, I'd try washing them. The grease came out with our regular detergent, nothing special added.
As for the mold and water issue. The mold problem stems from the door sealing when closed. As you may already know, all washers retain water in the pump. But typical top loaders don't seal the door like front loaders do. We just run a cup of bleach through ours every 3-4 months on the clean cycle.....runs about 20 min. No mold. Leaving the door cracked also stems the problem, but we have a Siamese that insists on sleeping inside the washer drum if left open. C'est la vie.
As for adding clothes to the washer after its started, ours allows you to do that, as do most front loaders, but only when it makes sense, like at the beginning of the wash cycle. Hit pause, the door unlocks, add clothes. However, further along in the cycle and it won't unlock unless you cancel the wash cycle completely. Then again, why would you want to add clothes to the washer after it's already beyond the wash cycle?
BTW.....they've been making all-in-one washer/dryer combo units for decades. They tend to be small, though. More for singles. Washer on the bottom, dryer on top.