If they're not marking the game up or down on that basis, but merely acknowledging the broader context of the product or review then what's the problem? That will be a factor that influences some people's purchases.
Does it bother you when 90% of games journalists acknowledge that their review copy was provided by the publisher? Or do you say they're being unprofessional and that if they want to talk about who provided the free code they should write a separate article? 'Cause, you know, where codes come from is either relevant or it isn't and shouldn't be included or should.