The reforms are part of the government's crackdown on so-called disguised employment, where workers behave as employees but avoid paying regular income tax and national income contributions by billing for their services through personal service companies, which are taxed at lower corporate rates.
This statement is entirely wrong. Only difference is that in case of out of scope contract, the client does not have to pay Employer's NI (which is correct, because they are not an employer).
The whole reform isn't about tax avoidance, but it was intended to remove competition of independent contractors that big consultancies (and party donors) were upset about.
That's why government shuts any conversation about it.