The seat post isn't slipping - there is a fundamental design problem with how the saddle clamp bolts are accessed.
Its next to impossible to access them without either scraping against the seat post or having the bit at an angle - neither of which are ideal, and should have been thought about before this design was approved.
For those who are visual like myself. You can see with the allen key, there is just enough space for it to be straight into the bolt. When you try to use a torque wrench, the head of the wrench and base of the socket hits the seat post. Causing the tool to sit slanted in the bolt and cause it to slip/round out the head. Possibly a longer allen socket would work but you would hope it works with what most people would have.
A revised seat post with better access to the bolts would be nice. Not a deal breaker but I can see it being annoying when building the bike.