What a peculiar discussion. I do hope nobody is being prejudiced against during recruitment for airline jobs because they don't separate their log book hours in accordance with an irrelevant criteria?
With respect, I think A Squared's quotes from the FAR 61.51 and the FAA's Chief Legal Counsel are a red herring. I don't think it's just a FAA thing either. I suspect many authorities have these out-of-date legislative passages and interpretations which don't fit with the modern airline operation.
Surely for airline pilots the 'outside conditions' would include the rules by which you are flying an airway, the radar heading assigned by ATC or the STAR/SID tracks? These rules do not require or imply any outside visual reference but they most certainly do require flying on instruments because without the instruments you could not comply.
Sub-dividing hours in to day/night and VMC/IMC conditions is quite possibly of relevance to GA or regional operators who fly primarily to small fields without instruments approaches, but to the airline industry it's arguable wholly irrelevant.