I suspect it's a case of if your product's good enough or cheap enough, poor instructions aren't actually a problem. Especially when people don't bother to read them anyway.
Look at pretty much every piece of consumer electronics produced in the far east over the last 20 years.
To pick a B&M example, there are, I think, about three actually important factoids in the IQ Cyo manual: The polarity of the wiring; the specification for running on DC and the correct behaviour of the Senso mode. Most people are only going to be interested in one or two of these, and none are rendered unclear as a result of sloppy translation or bad typesetting. The Cyo manual is Good Enough for something you only need to refer to during installation, and its inadequacies are overshadowed by an otherwise excellent product.
We have pretty low expectations for documentation, and I for one am delighted if it contains the information I'm looking for, whatever the language.
I'd also wonder what proportion of B&Ms sales are international. I suspect the vast majority are domestic, or to the Netherlands (where presumably overly germanic English isn't a problem).