Don’t get me wrong, the Trans-Provence is a tough week but it’s a million miles a way from the benchmark for a tough sport event.
Climbing is less than 2000m per day (some days more like 1000m) and untimed. If you’re reasonably fit then you can cruise this without too much effort at all. It’s incredibly scenic.
The special stages are amazing riding, some of the best trails on the planet, but they are not tremendously technical. Sure, they’re physical and riding them fast uses all your skills (and more) but they’re certainly not pushing the boundaries.
Trans-Provence is an amazing holiday and something which every serious biker should aspire to do but completing it doesn’t make you an extreme sportsman.
The most obvious sport which is “tougher” than mtb is road riding.