I know of and understand the spacing rules, but even one millimeter of (air) clearance can isolate up to 1500V if the board is clean (and more if you take solder mask into account). You can have as many design reviews as you want, and processes are very well and good, but they really don't answer the question of whether the design is sufficiently safe and reliable. Testing to failure is the only way to know what the product is capable of, as many designs have failure modes which are very difficult to imagine.

I agree the design doesn't comply with UL or IEEE standards, and that means it cannot be sold at retail in North America, but that doesn't mean the product is unreliable or unsafe.