That people get away with working while in B-1 or B-2 doesn't mean that the law allows it; simply put, some CBP officers know the law and others don't. The confusion is that years ago, the B-1 rules allowed for short term work in the U.S. while on the payroll of a foreign company but that absolutely isn't allowed anymore and if an applicant for a B-1 visa or admission in B-1 status says this, then there is a high probability that their visa application will be denied or they will be denied admission and possibly even banned. The grey area is the definition of "work" here. I use a couple of guidelines: clearly compensation from a U.S. source while in the U.S. is prohibited although reimbursement for reasonable travel expenses is allowed and activities the primary purpose of which is to benefit a U.S. entity or person almost certainly aren't allowed.