Apparently the answer to that question depends upon whom you ask. From an older RecruitingTrends.com article:
Furthermore, executives’ innate understanding of what defines flexible work strategies varies. While the largest percentage (45%) define it as pertaining to time, 31% view it as something to do with an employee’s location, and another 23% see flexible work arrangements as something other than time or location.
I would fall in the “Flexible location” group in terms of defining it. It would appear that this relatively new phrase requires a better definition. Or perhaps all new phrases and terms begin with some ambiguity.