> Is that specific to certain contracting status or is that the case for any kind of contracting?
It's specific for "sole proprietor" contractors. Multi-person operations, consultancies and bodyshops are exempt as long as the employees get their contributions paid.
> Obviously that means they are now acting company-like and have to pay social contribution like a company would but that should be on the contractor not on the client.
That is possible, indeed, you can voluntarily pay pension contributions (and that's the stuff that the pension fund claws back). You can also voluntarily contribute to the unemployment benefits.
As long as you at least pay the pension contributions, you're fine. The unemployment benefits is voluntary, no penalties if you don't pay these, but also, no payouts when you gotta close down shop.
The problem is, good luck finding a client willing to pay appropriate rates - too much unfair competition from those who just hope that neither they nor the client end up in a colonoscopy-level tax audit in 10 years (the time frame in which the statute of limitations for tax crimes expires), and the sad reality is that this gamble often enough pays off.