I think the laws regarding what you can or cannot call good is different in the EU than it is in the UK.
'Manufacturer refurbished' is a term often used, but in some cases I suspect 'refurbishment' may mean little more than an inspection, clean if required, reset and repackaging. 'B Grade is sometimes used, though I doubt the full legality, as once something has been sold it can never then be described as 'new', regardless of 'stock' or 'grade'.
I've bought a 'manufacturer refurbished' laptop, lawn mower and a pressure washer that way. Apart from one slight scratch on the laptop, all were 'like new', came with original packaging etc. The laptop had a 120 day warranty, the other items 6 months. Never a problem and saved a bundle, especially with the laptop which was less than half the price of a new one.
In the UK, there is no 30 day limit for return of faulty goods, in fact there's no time limit at all, though it's normally taken to be a year. In the first six months any faults are deemed to have been pre-existing when first bought. So these returns will eventually end up back with the manufacturer for refurbishment and eventual reselling.
When resold, I guess you might call them 'B stock' or 'C stock' in the USA.