There is no difference, its just sloppy use of language.

Reg 6 of the COSHH regs requires a risk assessment to be completed where work is liable to expose wokers to any substance hazardous to health.

why has this arisen? Poorly worded question on a PQQ or a new wet behind the ears inspector/auditor?

COSHH is not just 'risk assessment'. The first word in COSHH is 'Control'. Risk assessment is just the first step.

As the European Agency for Safety and Health at Work states; “A risk assessment is nothing more than a careful examination of what, in your work, could cause harm to people, so that you can weigh up whether you have taken enough precautions or should do more to prevent harm.”

Once you know what the risk is then you need to introduce measures to 'adequately control' the actual or potential exposure. Note what the regulation states: "Every employer shall ensure that the exposure of his employees to a substance hazardous to health is either prevented or, where this is not reasonably practicable, adequately controlled.' – Control of substances hazardous to health regulations, regulation 7(1)

Note that the 'reasonably practicable' only applies to 'prevention' and not to 'adequately control'. However, there is no official definition of what constitutes 'adequately control' other than a vague 'best practice' in the ACoP.  However, COSHH also covers health surveillance, a form of quality control to establish whether your control measures are working effectively.