Hello Roy
You are absoutely right. They shouldn't be offering this as a 'service'.
When you receive a confimed booking, it provides you with a phone number for BnB, so I would use this to flag what is happening with BnB. You can also use their social media and contact them through their resolution centre - again it gives you links to this on the confirmation of your guest's booking.
You can also 'red flag' this guest and tell BnB that they have set up a business to book BnB rooms on behalf of other guests.
This is a real problem as you have no idea who the guests are and you won't be covered under their guarantee.
BnB should ban the person running a business in this way.
Of course if this is a business and there is a PA and other person booking on behalf of their staff, this would be fine.