Yes, that is a big plus. The heavier duty chain and sprockets suits ebikes very well. I usually have two chains which I swap over from time to time. After trying many different fancy lubricants, I've found a liberal coating of grease the best. I then just clean it off and re-grease when I swap the chains over, not swapping the sprockets until teeth start falling off.
You really need wider sprockets for any advantage of the wider chains.
They also claim an efficiency of circa 99% for their hub gear which is completely impossible!
There are various reasons for using a tensioner with hub gear or single speed bikes. One is using a derailleur type dropout frame which has no sliding adjustment for the rear wheel. This is sometimes done for the superior wheel alignment of such frames or avoiding the fundamental weakness of spindle slide slots in frames.
And of course there's the alternative menthod of chain tensioning with a vertical dropout frame, using an eccentric bottom bracket like these.
I think my bike would probably be scrap now if I hadn't fitted a tensioner. There was someone on here a few years ago who ended up with nearly destroyed horizontal drop-outs in a very short space of time.
Yes, some frame designs and materials were substandard. The otherwise excellent Giant Lafree series suffered from soft alloy dropout material that stretched the frame slots wider over time.
