It is not a bad deal to get a clean, fully functioning, shooter mauser in K98 configuration. The issue is whether that they are/were marketed as being more or less authentic, when in reality they are parts guns. And some, like M48 Yugos, had absolutely no WWII involvement.
Most issued K98s saw the worst possible scenario. I have read, that when German units surrendered en masse, that bolts went into one pile, the rest of the mauser in another. No effort was ever made to keep these weapons as usable, until some time later when demand increased for them in places like Israel, Africa, Asian proxy wars, etc.
I will not own any post WW I German made mausers. They are simply too difficult to find in any kind of 'known' condition, and often demand prices out of proportion to their value as a shooter owing to the WWII mystique.
Swedish Mausers, South American Contract Mausers, Turks, Yugos all were much easier to find in collectable condition simply because these weapons were never used in war.
So, as for Mitchell's Mauser being a 'WWII war relic', it's probable that parts of any given one are of that vintage. For them to claim anything else is just making stuff up.