Dave,
It is true that without the presence of the micro-fungi the dust mite cannot survive as the ex foliated skin will not contain sufficient water to sustain them.
Again, it is the penetration depth of the light that makes me sceptical of its' value, and the fact is that any reduction in the mould colony would very very temporary.
Good practise by the customer - leaving bedding exposed to fresh, cool, dry air for a couple of hour per day will have far more beneficial effect.