Bikes designed for different disciplines of riding need a different design. The Saracen Xile you mentioned above was a dirt jump bike. It was marketed at kids who wanted to spend hours jumping off unsuitable things. Of course it would be stronger than a bike designed for cross country. I am surprised that someone who obviously spends so much time thinking about bikes hasn't considered this.
The Hoss was supposed to be an XC bike for heavier riders - see the Wayback Machine description of it from Kona's website here. A stronger frame than an XC bike (look at those massive square tubes!) and a much more forgiving riding position than any of its contemporaries. A heavy rider could well have damaged a lighter XC frame, and they would likely have found it uncomfortable in any case.
There will be plenty of examples of unused bikes out there - the road to hell is paved with good intentions. If OP can find one, a Hoss will be a good choice with the parts that were specified by the manufacturer - it was designed for a heavier rider who probably has less bike fitness. It's much more upright than an XC bike from the same period.
As to weight limits on modern MTBs - I strongly suspect the figure is pretty arbitrary, specified by the warranty department as much as design. You just don't hear of big people breaking mid-range bike frames very often - superlight stuff maybe, but that's not what we're discussing here.
Wheels fail, in the most part. This is because they're not usually not specced properly, and built by machine. Partly it's rider weight and distribution between front and back wheels, partly because inexperienced riders don't learn to unweight themselves over the bike when they go over potholes. In either case, this can be mitigated by choosing appropriate components. 36 spokes on the rear wheel, stronger spokes on the cassette side and stress relief and retensioning before the bike gets ridden on.
