Why do Fire Policies ban 'Under-desk heaters' instead of defining the heater type?

A question for those involved in writing, auditing, or enforcing workplace fire policies:

Why do so many policies prohibit "under-desk heaters" rather than defining the specific heating technologies that create the risk?

In my experience, the phrase "under-desk heater" is often used as a catch-all term, but it can cover a wide range of products that operate very differently.
For example, a portable 2kW fan heater and a 2kW convector heater are commonly restricted in workplaces, and it's easy to understand why organisations may be concerned about high-power portable appliances being used in confined spaces around cables, paper, bags and other combustible materials.

However, newer heating technologies have emerged that don't rely on warm air circulation or convection. Some use far-infrared heat, operate at significantly lower power levels, and have no fans or air movement.

Should workplace policies continue to focus on the location ("under desk"), or would it be more appropriate to focus on the heating method, power consumption, and overall risk profile of the appliance?

I'm genuinely interested in how fire risk assessors, insurers, facilities managers and H&S professionals approach this.

Are blanket bans on "under-desk heaters" still the right approach, or should policies evolve to distinguish between different technologies?

Interested to hear different perspectives, especially from those who have had to justify these policies following a risk assessment.