Re: Just the start
The fear is not of commitment, particularly for the specialist subject matter expert. The fear is of finishing up getting less benefits from your contract than a conventional employee but still under instruction from a boss that brought you in as an expert because they didn't understand the subject, or from an agency that understands even less.
I can't see why this isn't crystal clear to all who discuss the matter. It's the fundamental difference between a contract of service (employment) and a contract for services (B2B consulting), and all IR35 is doing is muddying the waters and killing off the independent consulting option, which is essential for business in many circumstances. Soon, the only consultants left will be employees of the big four who by definition fall outside IR35. So they'll grab the entire market while continuing to mess up repeatedly.