There is a fine line between conducting business and working. Conducting business is allowed as a business visitor, working, even if you are getting paid abroad, is technically illegal. So attending business meetings, attending conferences, advising, etc. are allowed, pretty much everything else is essentially not allowed.
IOs have always been hesitent to bounce people who come as "business visitors" but aren't, because it is generally bad for business relations, but I highly suspect we are going to see people questioned on how they can be coming over for "months" at a time and not performing work. Especially since for Visa nationals they are specifically introducing the business visitor category with certain requirements.